PTCB Math Formulas: Current PTCE Study Sheet
This unofficial study sheet covers the core formulas and number-based rules behind the calculation areas on PTCB's PTCE content outline, in effect since January 6, 2026. You get a built-in calculator on exam day but you can't bring your own notes, so know these cold. Alligation isn't here on purpose — see why.
The study sheet
Every worked example below is our own arithmetic with made-up training numbers. The examples teach math, not dosing.
Conversions
| Formula | Use it when | Worked example |
|---|---|---|
| Value × (new unit ÷ old unit), set up so the old unit cancels | Any unit change | 0.4 g × (1,000 mg ÷ 1 g) = 400 mg |
| 1 kg = 1,000 g · 1 g = 1,000 mg · 1 mg = 1,000 mcg · 1 L = 1,000 mL | Moving along the metric ladder: each step is × or ÷ 1,000 | 2,500 mcg ÷ 1,000 = 2.5 mg |
| kg = lb ÷ 2.2 | Turning a patient weight into kilograms | 132 lb ÷ 2.2 = 60 kg |
| °C = (°F − 32) ÷ 1.8 · °F = (°C × 1.8) + 32 | Storage temperatures | (77 − 32) ÷ 1.8 = 25 °C |
| 1 tsp = 5 mL · 1 tbsp = 15 mL · 1 fl oz = 30 mL | Household units in a sig | 2 tsp = 10 mL |
| Roman numerals: i = 1, v = 5, x = 10, l = 50, c = 100. A smaller numeral before a larger one subtracts. | Quantities written on prescriptions | "tabs iii" = 3; "#xxiv" = 24; "ix" = 9 |
Metric prefixes and the temperature formula come from NIST SP 1038 (Table 2; §5.3.1 footnote 33). The 2.2 and household values are rounded conventions — more precise conversion values are in the table below.
Doses and quantities
| Formula | Use it when | Worked example |
|---|---|---|
| Dose volume = (Desired ÷ Have) × Quantity — often written D/H × Q | Finding mL or tablets for a dose from a stock strength | Order 300 mg; stock 250 mg/5 mL → (300 ÷ 250) × 5 = 6 mL |
| Dose = mg/kg × weight in kg | Weight-based orders | 15 mg/kg × 20 kg = 300 mg |
| Per-dose amount = daily amount ÷ doses per day | Orders written "per day, in divided doses" | 300 mg/day ÷ 3 doses = 100 mg per dose |
| Doses per day = 24 ÷ interval in hours | Around-the-clock orders like q6h or q8h | q6h → 24 ÷ 6 = 4 doses/day |
| Quantity = amount per dose × doses per day × days | Filling a fixed course | 1 cap × 3/day × 10 days = 30 caps |
Three checks that catch most mistakes here:
- D and H must be in the same unit before you divide. Convert mg to mcg (or the reverse) first.
- Read "mg/kg/day" and "mg/kg/dose" twice. Confusing them multiplies or divides your answer by the number of daily doses.
- If a schedule changes partway through (a taper), work out each phase separately and add them.
Days' supply
| Formula | Use it when | Worked example |
|---|---|---|
| Days' supply = quantity dispensed ÷ quantity used per day | Tablets and capsules | #60, 1 tab bid → 60 ÷ 2 = 30 days |
| Liquids: total mL ÷ (mL per dose × doses per day) | Oral liquids | 200 mL, 5 mL tid → 200 ÷ 15 = 13.3 → lasts 13 full days |
| Drops: (bottle mL × drops per mL) ÷ drops used per day | Eye and ear drops | 10 mL × 20 gtt/mL = 200 drops; 2 drops a day → 100 days |
| Insulin: (mL in package × units per mL) ÷ units used per day | Vials and pens | 3 mL × 100 units/mL = 300 units; 30 units a day → 10 days |
| Inhalers: labeled actuations ÷ actuations used per day | Metered-dose inhalers | 120 actuations, 2 puffs bid → 120 ÷ 4 = 30 days |
Keep these conditions beside the formulas:
- Drops per mL varies by product. Use the number the question gives you. There's no single standard.
- Insulin strength is on the label. U-100 means 100 units per mL; U-200, U-300, and U-500 also exist (American Diabetes Association).
- If a question adds priming units or a discard period, include them. The shorter limit wins.
- A partial day isn't a full day. 13.3 days of medicine lasts 13 full days. Real claims can follow payer rules, so answer what the question asks.
Concentration and dilution
| Formula | Use it when | Worked example |
|---|---|---|
| % w/v = grams per 100 mL · % w/w = grams per 100 g · % v/v = mL per 100 mL | Reading any percent strength — check which basis it is | 0.9% w/v = 0.9 g in 100 mL |
| Grams in a volume = (% ÷ 100) × volume | "How much drug is in…" | 5% w/v, 500 mL → 0.05 × 500 = 25 g |
| mg/mL = % (w/v) × 10 | Turning a w/v percent into mg/mL | 2% w/v = 20 mg/mL |
| mg/g = % (w/w) × 10 | Creams and ointments labeled w/w | 1% w/w = 10 mg per gram (not per mL) |
| Concentration = amount of drug ÷ final volume | After reconstituting or mixing | 900 mg in a final 150 mL → 6 mg/mL |
| Ratio strength 1:x (w/v) = 1 g in x mL | Older ratio labels | 1:1,000 = 1 g/1,000 mL = 1 mg/mL |
| C₁ × V₁ = C₂ × V₂, so V₁ = (C₂ × V₂) ÷ C₁ | Diluting a stock to a weaker strength | 10% stock → 200 mL of 2%: (2 × 200) ÷ 10 = 40 mL of stock, made up to 200 mL |
Three conditions matter here:
- The percent-to-mg/mL shortcut only works for w/v. A w/w cream is grams per 100 grams, so its answer is mg per gram. Never swap the basis silently. The definitions come from USP General Notices 8.140.
- V₂ is the final total volume, not the amount of diluent you add. In the example, you measure 40 mL of stock and add diluent up to 200 mL. Only if a question tells you to treat volumes as simply adding up would the diluent be 200 − 40 = 160 mL. The dilution equation assumes the drug amount stays the same while the volume changes (OpenStax Chemistry 2e §3.3).
- Reconstituted products use the final volume on the label, not the diluent volume. If 32 mL of diluent makes 40 mL of suspension, divide by 40.
USP now requires single-entity injections to show strength as mg/mL instead of a ratio. For example, epinephrine once labeled 1:1,000 is labeled 1 mg/mL (USP ⟨7⟩ Labeling). Ratio math still helps you read older references.
IV rates (a supporting skill)
PTCB's current outline doesn't name IV rates. They use the same volume-over-time arithmetic as days' supply, so they get a small spot here.
| Formula | Use it when | Worked example |
|---|---|---|
| mL/hr = total mL ÷ hours | Infusion rate | 500 mL ÷ 4 hr = 125 mL/hr |
| gtt/min = (mL × drop factor) ÷ minutes | Gravity drip rate; the drop factor (gtt/mL) is printed on the tubing and given in the question | (480 × 15) ÷ 240 min = 30 gtt/min |
| Hours = total mL ÷ mL/hr | "When will it finish?" | 1,000 ÷ 125 = 8 hr |
Convert hours to minutes before using the drip formula. The drop factor is drops per mL, not drops per minute.
Rules with numbers in them
Several of PTCB's calculation-marked areas (1.7, 2.2, 2.4, and 4.3) are rules, not formulas. The math is short, but the numbers come from regulations.
| Rule | How the math works | Worked example |
|---|---|---|
| Schedule III–IV prescriptions: may not be filled or refilled more than 6 months after the issue date, and may not be refilled more than 5 times (21 CFR 1306.22) | Whichever limit arrives first ends the prescription | Issued January 15 with 5 refills → nothing may be filled after July 15, even if refills remain |
| Pseudoephedrine limits count base, not salt: retail sales are limited to 3.6 g of base per purchaser per day; an individual may not purchase more than 9 g in 30 days, of which no more than 7.5 g may be acquired by shipping through a private/commercial carrier or the U.S. Postal Service (DEA; 21 U.S.C. §844) | A 30 mg pseudoephedrine HCl tablet contains less than 30 mg of pseudoephedrine base, so more tablets fit under the base limit than 3,600 ÷ 30 | DEA's official chart gives 146 tablets of 30 mg pseudoephedrine HCl at the 3.6 g daily base limit (DEA Chemical Handler’s Manual, Appendix I) |
| NDC billing format (11 digits, 5-4-2): add one leading zero to the short segment of the 10-digit NDC (FDA, slides 4–6) | 4-4-2 → pad the labeler · 5-3-2 → pad the product · 5-4-1 → pad the package | 12345-678-90 → 12345-0678-90 |
| Month/year expiration = the last day of that month (USP ⟨7⟩) | Count to month-end and check leap years | EXP 04/2027 → good through April 30, 2027 |
| Reconstituted products: the label sets the discard date | The mixed product's clock, not the stock bottle's expiration | Amoxicillin oral suspension labels say to discard unused suspension after 14 days (DailyMed) |
Federal rules set the floor. Your state can add stricter refill or pseudoephedrine limits.
The NDC format is scheduled to change. FDA's final rule moves every NDC to one 12-digit format (6-4-2) on March 7, 2033. Until then, FDA keeps assigning the 10-digit formats above (FDA).
Notation that causes tenfold errors
- Always use a leading zero: 0.5 mg, never .5 mg.
- Never add a trailing zero: 5 mg, never 5.0 mg.
- Write units, not U, and mcg, not µg.
- Ear and eye abbreviations (AD/AS/AU and OD/OS/OU) get swapped, so the safest practice is to write them out.
These come from the ISMP List of Error-Prone Abbreviations (2024). PTCB's outline names leading and trailing zeros in its error-prevention area.
Exact values vs. the shortcuts problems use
Use the factor the question gives you. If it gives none, use the shortcut column — it's the rounded value pharmacy math problems almost always use.
| Relationship | Shortcut | More precise / defined value | Notes |
|---|---|---|---|
| 1 kg | 2.2 lb | ≈2.20462 lb (1 lb = 0.45359237 kg exactly) | ÷ 2.2 is standard in problems |
| 1 teaspoon | 5 mL | 1/6 fl oz (NIST's practical equivalent: 5 mL) | FDA's labeling convention is also 5 mL |
| 1 tablespoon | 15 mL | 1/2 fl oz (practical equivalent: 15 mL) | 3 tsp = 1 tbsp |
| 1 fluid ounce | 30 mL | 29.57 mL | 30 mL is the federal labeling convention |
| 1 pint | 473 mL | 473.18 mL | |
| 1 gallon | 3,785 mL | 3,785.41 mL | |
| 1 ounce (weight) | 28 g or 28.35 g | 28.34952 g | Problems usually say which to use |
| 1 grain | 65 mg (rounded) | 64.79891 mg | Rare now; use the question's factor |
| 1 cup | Avoid | 8 fl oz | NIST's practical 250 mL and FDA's labeling 240 mL disagree |
The more precise and defined values are from NIST SP 1038 (§5.1.5 and footnote 19; §5.2.1). The labeling conventions are from 21 CFR 101.9(b)(5)(viii), which governs food labels. The rounded figures in the more-precise column are our arithmetic from the cited definitions and factors.
How to pick the right formula
Most wrong answers use real numbers in the wrong setup. Four steps prevent that:
- Write the unit you want first — mL per dose, tablets, days, mg/mL, or gtt/min. The answer unit tells you the formula.
- Translate the sig into plain words and put every quantity in matching units.
- Set it up so unwanted units cancel. Don't round until the last step.
- Check the scale. A daily amount can't answer a per-dose question, and a final volume can't answer "how much stock?"
Practice: 20 original PTCB math problems
These are original Castleport practice problems, not official PTCE questions. Numbers are made up for training. Use the factors and rounding given in each problem. A score here is feedback on these 20 items, not a PTCE score or a prediction.
PM-01 · Metric conversion An order calls for 0.18 mg. Each tablet contains 90 mcg. How many tablets is that?
A. 0.002 tablet B. 0.5 tablet C. 2 tablets D. 20 tablets
Hide or reveal answer and rationale
Answer: C — 2 tablets. Convert first: 0.18 mg × 1,000 = 180 mcg. Then 180 mcg ÷ 90 mcg per tablet = 2 tablets. A divides mg by mcg without converting. B flips the ratio. D is a tenfold conversion slip. Matching units before dividing is the whole problem. Source: NIST SP 1038, Table 2.
PM-02 · Temperature A thermometer reads 46.4 °F. What is that in °C?
A. 8 °C B. 14.4 °C C. 25.8 °C D. 115.5 °C
Hide or reveal answer and rationale
Answer: A — 8 °C. (46.4 − 32) ÷ 1.8 = 14.4 ÷ 1.8 = 8 °C. B stops after subtracting 32. C divides by 1.8 without subtracting 32 first. D uses the °C-to-°F formula on a Fahrenheit reading. Source: NIST SP 1038, footnote 33.
PM-03 · Household units Sig: 1 tbsp po tid. How many mL does the patient take per day?
A. 15 mL B. 45 mL C. 30 mL D. 90 mL
Hide or reveal answer and rationale
Answer: B — 45 mL. 1 tbsp = 15 mL, and tid means three times a day: 15 × 3 = 45 mL. A is one dose. C treats tid as twice daily. D uses 30 mL for a tablespoon — that's a fluid ounce. Source: NIST SP 1038, footnote 19.
PM-04 · Dose volume An order calls for 375 mg. The stock is 250 mg/5 mL. How many mL per dose?
A. 1.5 mL B. 3.3 mL C. 75 mL D. 7.5 mL
Hide or reveal answer and rationale
Answer: D — 7.5 mL. (375 ÷ 250) × 5 = 7.5 mL. B flips desired and have. A forgets to multiply by the 5 mL. C divides the dose by 5 mL. Sense check: the dose is 1.5 times the stock's 250 mg, so the volume should be 1.5 times 5 mL. Source: our arithmetic.
PM-05 · Weight-based dose A patient weighs 44 lb. The order is 15 mg/kg/day, divided every 8 hours. Using 2.2 lb = 1 kg, how many mg is each dose?
A. 100 mg B. 220 mg C. 300 mg D. 900 mg
Hide or reveal answer and rationale
Answer: A — 100 mg. 44 ÷ 2.2 = 20 kg. 15 × 20 = 300 mg per day. Every 8 hours means 3 doses: 300 ÷ 3 = 100 mg. B treats pounds as kilograms (44 × 15 ÷ 3). C is the daily total. D multiplies by 3 instead of dividing. Source: our arithmetic.
PM-06 · Days' supply, tablets Dispense #45. Sig: 1½ tabs po bid. What is the days' supply?
A. 22 days B. 30 days C. 15 days D. 45 days
Hide or reveal answer and rationale
Answer: C — 15 days. 1.5 tablets × 2 doses = 3 tablets a day. 45 ÷ 3 = 15 days. A divides by 2 and ignores the half tablet. B divides by 1.5 and ignores bid. Source: our arithmetic.
PM-07 · Quantity to dispense Sig: 2 caps po q6h around the clock × 7 days. How many capsules should be dispensed?
A. 14 B. 28 C. 42 D. 56
Hide or reveal answer and rationale
Answer: D — 56. Every 6 hours around the clock is 24 ÷ 6 = 4 doses a day. 2 × 4 × 7 = 56. A uses one dose a day. B uses one capsule per dose. C uses three doses a day. Source: our arithmetic.
PM-08 · Changing schedule Sig: 2 tabs once daily for 3 days, then 1 tab once daily for 4 days. How many tablets cover the whole course?
A. 7 B. 10 C. 11 D. 14
Hide or reveal answer and rationale
Answer: B — 10. Work each phase: (2 × 3) + (1 × 4) = 6 + 4 = 10. A treats every day as a one-tablet day. C swaps the phases' lengths. D keeps 2 tablets a day for all 7 days. Source: our arithmetic.
PM-09 · Eye drops A 5 mL bottle. The problem specifies 20 drops per mL. Sig: 1 gtt OU bid. Ignore waste and discard limits. What is the days' supply?
A. 12 days B. 50 days C. 25 days D. 100 days
Hide or reveal answer and rationale
Answer: C — 25 days. 5 mL × 20 = 100 drops. OU means each eye, so 1 drop × 2 eyes × 2 times = 4 drops a day. 100 ÷ 4 = 25 days. B counts one eye. A doubles the daily use again. D treats each drop as a day. Source: our arithmetic; abbreviation note from ISMP.
PM-10 · Insulin A 10 mL vial of U-100 insulin. The patient injects 30 units every morning and 20 units at bedtime. Ignore priming and any discard period. What is the days' supply?
A. 20 days B. 33 days C. 50 days D. 10 days
Hide or reveal answer and rationale
Answer: A — 20 days. U-100 means 100 units per mL, so the vial holds 10 × 100 = 1,000 units. Daily use is 30 + 20 = 50 units. 1,000 ÷ 50 = 20 days. B counts only the morning dose. C is the daily units, not days. D is the vial's mL. Source: American Diabetes Association.
PM-11 · Percent strength (w/v) How many grams of dextrose are in 1,000 mL of a dextrose 5% (w/v) solution?
A. 5 g B. 50 g C. 200 g D. 500 g
Hide or reveal answer and rationale
Answer: B — 50 g. 5% w/v means 5 g per 100 mL. 1,000 mL is ten 100-mL portions, so 5 × 10 = 50 g. A is the amount in 100 mL. C divides 1,000 by 5. D treats 5% as 50 g per 100 mL. Source: USP General Notices 8.140.
PM-12 · Percent strength (w/w) A cream is 0.6% (w/w). How many mg of the active ingredient are in 12 g of cream?
A. 7.2 mg B. 720 mg C. 0.72 mg D. 72 mg
Hide or reveal answer and rationale
Answer: D — 72 mg. 0.6% w/w = 0.6 g per 100 g. (0.6 ÷ 100) × 12 g = 0.072 g = 72 mg. A and C are ten and a hundred times too small; B is ten times too large. The basis is grams of cream, so no mL appear anywhere. Source: USP General Notices 8.140.
PM-13 · Ratio strength An older reference lists a solution as 1:1,000 (w/v). What is that in mg/mL?
A. 0.1 mg/mL B. 1 mg/mL C. 10 mg/mL D. 1,000 mg/mL
Hide or reveal answer and rationale
Answer: B — 1 mg/mL. 1:1,000 w/v = 1 g in 1,000 mL = 1,000 mg in 1,000 mL = 1 mg/mL. A is 1:10,000. USP requires single-entity injectable strengths to be expressed as quantity per milliliter rather than as a ratio. Source: USP ⟨7⟩ Labeling.
PM-14 · Dilution How many mL of a 20% stock solution are needed to make 400 mL (final volume) of a 5% solution?
A. 80 mL B. 300 mL C. 100 mL D. 1,600 mL
Hide or reveal answer and rationale
Answer: C — 100 mL. C₁V₁ = C₂V₂ → 20 × V₁ = 5 × 400 → V₁ = 100 mL of stock, made up to 400 mL. B is 400 − 100, which would be the diluent only if volumes simply add. A takes 20% of 400. D flips the ratio. Sense check: 5% is a quarter of 20%, so the stock is a quarter of the final volume. Source: OpenStax Chemistry 2e §3.3.
PM-15 · Reconstitution A training label says a vial holds 1.2 g of powder, and adding 32 mL of diluent makes 40 mL of final solution. What volume of the final solution contains 300 mg?
A. 0.25 mL B. 8 mL C. 30 mL D. 10 mL
Hide or reveal answer and rationale
Answer: D — 10 mL. 1.2 g = 1,200 mg. Final concentration: 1,200 mg ÷ 40 mL = 30 mg/mL. Volume: 300 ÷ 30 = 10 mL. B divides by the 32 mL of diluent instead of the 40 mL final volume. A stops at the fraction 300 ÷ 1,200. C is the concentration, not a volume. Source: our arithmetic.
PM-16 · Drip rate 1,000 mL is to infuse over 8 hours with a 15 gtt/mL set. What is the drip rate, rounded to the nearest whole drop per minute?
A. 31 gtt/min B. 125 gtt/min C. 21 gtt/min D. 1,875 gtt/min
Hide or reveal answer and rationale
Answer: A — 31 gtt/min. 8 hours = 480 minutes. (1,000 × 15) ÷ 480 = 31.25, which rounds to 31. B is the mL/hr rate. C uses a 10 gtt/mL factor. D divides by hours instead of minutes. Source: our arithmetic.
PM-17 · NDC format A package shows NDC 1234-5678-90. What is the 11-digit (5-4-2) billing format?
A. 12340-5678-90 B. 01234-5678-90 C. 1234-05678-90 D. 1234-5678-090
Hide or reveal answer and rationale
Answer: B — 01234-5678-90. This is a 4-4-2 NDC, so the labeler segment is short by one digit. Add one leading zero there. A adds a trailing zero, which changes the number. C and D pad segments that are already full length. Source: FDA, slides 4–6.
PM-18 · Expiration dating A stock bottle is labeled EXP 02/2028. Under USP labeling standards, what is the last day it's good?
A. January 31, 2028 B. February 1, 2028 C. February 29, 2028 D. February 28, 2028
Hide or reveal answer and rationale
Answer: C — February 29, 2028. A month/year expiration means the last day of that month. 2028 is divisible by 4, so it's a leap year and February ends on the 29th. D is the trap. Source: USP ⟨7⟩ Labeling.
PM-19 · Controlled substance refills A Schedule IV prescription for a 90-day supply is issued March 3 with 5 refills. The patient fills it March 3, then refills each time the supply runs out (June 1, August 30, and so on). Under federal rules, how many refills can be dispensed?
A. 1 B. 2 C. 3 D. 5
Hide or reveal answer and rationale
Answer: B — 2. Federal law says a Schedule III or IV prescription may not be filled or refilled more than six months after the issue date — here, after September 3. June 1 and August 30 fall inside that window. The next date, November 28, doesn't. So only 2 of the 5 authorized refills can be used. This item tests the federal rule only. Source: 21 CFR 1306.22(a).
PM-20 · Pseudoephedrine 3.6 g ÷ 30 mg = 120 tablets, yet DEA's chart allows 146 tablets of 30 mg pseudoephedrine HCl per day. Why?
A. States add a buffer to the federal limit. B. Box sizes are rounded up. C. The daily limit is really 4.38 g. D. The limit counts pseudoephedrine base, and each 30 mg salt tablet contains less than 30 mg of base.
Hide or reveal answer and rationale
Answer: D. Federal limits are measured as base. The HCl salt includes the weight of the hydrochloride, so each tablet carries less base than its label strength, and more tablets fit under 3.6 g. C is 146 × 30 mg of salt, not base. A and B aren't how the limit works. Sources: DEA CMEA limits; DEA Chemical Handler’s Manual, Appendix I.
Answer key
| Item | Answer | Item | Answer |
|---|---|---|---|
| PM-01 | C | PM-11 | B |
| PM-02 | A | PM-12 | D |
| PM-03 | B | PM-13 | B |
| PM-04 | D | PM-14 | C |
| PM-05 | A | PM-15 | D |
| PM-06 | C | PM-16 | A |
| PM-07 | D | PM-17 | B |
| PM-08 | B | PM-18 | C |
| PM-09 | C | PM-19 | B |
| PM-10 | A | PM-20 | D |
Missed one? Go back to its row on the study sheet, rework the example there, then try the problem again tomorrow without looking.
Is alligation still on the PTCB exam?
Not as a listed topic. When PTCB announced the current outline, it said it was removing nonsterile compounding content along with "alligations" from the old calculation area (PTCB job analysis notice). The current outline's calculation area (4.1) no longer mentions it. Dilution is still there.
You may still see alligation in PTCB's broader 2026 CPhT Knowledge Reference. That document maps the whole job, not just the exam. It lists alligation under nonsterile compounding calculations in its "recommended" band — knowledge PTCB suggests but doesn't require, and doesn't list as a PTCE area (p. 5).
That isn't a promise that mixing math can never appear. If you already know the method, keep it. If you don't, learn the formulas above first.
Formulas in older guides that the current outline doesn't name
| Formula | Named in the current PTCE outline? | Where PTCB's Knowledge Reference puts it | Our take |
|---|---|---|---|
| Alligation (mixing two strengths) | No — removed January 6, 2026 | Recommended, under nonsterile compounding | Low priority |
| Clark's Rule and Young's Rule (pediatric estimates) | No | Not named | Low priority |
| Body surface area (Mosteller) and mg/m² dosing | No | Not named | Low priority |
| Markup, AWP, and dispensing-fee math | No | Billing and reimbursement: recommended only | Skip for the PTCE |
| DEA number check digit | No | Lists electronically verifying a DEA or NPI number as required knowledge shown outside the exam — not a check-digit formula | Skip for the PTCE |
| Milliequivalents | No | Not named | Low priority |
"Not named" means not named. It isn't a guarantee a topic will never appear. To see where any topic lands, search it in our free PTCE Scope Check.
Can you bring a formula sheet or use a calculator?
You can't bring your own sheet. PTCB's Candidate Agreement (item 14) says you may not refer to any materials other than those provided to you during the exam. PTCB's policies we checked don't mention a formula or conversion sheet being provided, so plan to work from memory. Use this page to study, not as something to carry in.
You do get a calculator. One is built into the exam. You can't use your own. If you ask for a hand-held calculator and the test center has one, you may use it (PTCB calculator policy). Practice with an on-screen calculator so it doesn't slow you down on test day.
PTCB doesn't publish how many questions involve math. Its outline flags calculation-based knowledge in nine areas across all four domains, but it gives no question count. Our PTCB exam prep hub maps those areas.
Quick answers
Is 1 kg 2.2 lb or 2.2046 lb? 1 kg is approximately 2.20462 lb. Pharmacy-math problems commonly tell you to use 2.2, and you should use the factor the question gives.
How do you round days' supply? A supply lasts only its full days, so 13.3 days is 13. If a question states its own rounding rule, follow it.
Which PTCB math formulas matter most? PTCB doesn't rank them. In our judgment, days' supply, D/H × Q, and C₁V₁ = C₂V₂ cover the most of what area 4.1 lists: days' supply, quantity, dose, concentration, and dilution.
Sources and verification
What we checked, September 24, 2026: PTCB's PTCE Content Outline v1.4 (effective January 6, 2026, both pages); PTCB's PTCE job analysis notice; PTCB's 2026 CPhT Knowledge Reference (all eight pages) and 2020 Knowledge Reference (Order Entry section); PTCB's Calculators policy (updated June 24, 2025) and Candidate Agreement v3.1; NIST SP 1038; 21 CFR 101.9(b)(5)(viii); USP General Notices 8.140; USP ⟨7⟩ Labeling; OpenStax Chemistry 2e §3.3; 21 CFR 1306.22; DEA's CMEA page and tablet chart; FDA's NDC format page and NDC presentation; ISMP's 2024 error-prone abbreviation list; the American Diabetes Association's insulin concentration overview; and DailyMed amoxicillin suspension labeling. Every worked example and practice answer was recalculated during this audit; the 20-item numerical key was also checked programmatically. "Low priority" and "skip" are our editorial judgments, not PTCB's.
By Castleport Test Prep Editorial Team · Last verified: September 24, 2026 · Methodology · Corrections log
Castleport Test Prep is an independent exam prep publisher and is not affiliated with, endorsed by, or approved by the Pharmacy Technician Certification Board (PTCB). Exam and credential names such as PTCE and CPhT identify the exam and credential discussed; trademarks belong to their respective owners. The practice problems are original and unofficial, not PTCE questions. This page teaches exam math. It is not dosing advice or a guarantee of passing.