Tablet and Capsule Calculations
Solid dosage forms use the same Desired Over Have setup as liquids, with Q usually equal to 1 tablet or 1 capsule.
In this lesson
- Setting up tablet and capsule problems
- Converting units before counting tablets
- How half-tablet problems are written
- Why capsule answers are whole numbers
What you're solving for
The number of tablets or capsules that contain the ordered dose.
Desired divided by Have, times 1 tablet, equals the number of tablets
Worked examples
Example 1: Whole tablets
Ordered: 100 mg. On hand: 50 mg tablets.
Step 1: Calculation
100 mg ÷ 50 mg × 1 tablet
= 2 tablets
Step 2: Formula
Desired ÷ Have × Quantity = Amount
Step 3: Check your units
mg cancels with mg, leaving tablets.
Answer: 2 tablets
Example 2: Convert mg to mcg first
Ordered: 0.2 mg. On hand: 100 mcg tablets.
Step 1: Unit conversion
0.2 mg = 200 mcg
Step 2: Calculation
200 mcg ÷ 100 mcg × 1 tablet
= 2 tablets
Step 3: Formula
Desired ÷ Have × Quantity = Amount
Step 4: Check your units
mcg cancels with mcg, leaving tablets.
Answer: 2 tablets
Example 3: Capsules
Ordered: 500 mg. On hand: 250 mg capsules.
Step 1: Calculation
500 mg ÷ 250 mg × 1 capsule
= 2 capsules
Step 2: Formula
Desired ÷ Have × Quantity = Amount
Step 3: Check your units
mg cancels with mg, leaving capsules.
Answer: 2 capsules
Half tablets in educational problems
Some problems produce a half tablet. Dosage Calcs only uses one when the problem says so directly:
Example 4: A scored tablet
Ordered: 12.5 mg. On hand: 25 mg tablets. For this educational problem, the tablet is scored and may be divided in half.
Step 1: Calculation
12.5 mg ÷ 25 mg × 1 tablet
= 0.5 tablet
Step 2: Formula
Desired ÷ Have × Quantity = Amount
Step 3: Check your units
mg cancels with mg, leaving tablets.
Whether an actual tablet may be split depends on the specific product and applicable instructions or policy.
Answer: 0.5 tablet
Some tablets, including certain extended-release or otherwise specially formulated products, should not be split. Whether a specific tablet may be divided depends on the product and its labeling or instructions. Never assume a tablet may be split simply because the calculation produces a fractional tablet — recheck the order and product information.
Capsules stay whole
Capsules are not divided, so capsule problems on Dosage Calcs always work out to whole capsules. If a capsule calculation gives a fraction, recheck the numbers and units — the Dosage Calculator flags this too.
Common mistakes
Skipping the unit check
- What goes wrong
- 0.2 mg ÷ 100 mcg × 1 tablet = 0.002 tablet
- Why it fails
- mg and mcg were divided directly.
- Correct approach
- 0.2 mg = 200 mcg; 200 mcg ÷ 100 mcg × 1 tablet = 2 tablets
Quick self-check
Ordered 1 g; on hand 500 mg tablets. How many tablets?
Show the answer
1 g = 1,000 mg; 1,000 mg ÷ 500 mg × 1 tablet = 2 tablets
Calculate and practice
Related lessons
- Desired Over Have (D ÷ H × Q) — The D ÷ H × Q formula for tablets, capsules and liquids.
- Liquid Medication Calculations — Read a concentration correctly and calculate the mL.
- Rounding & Number Safety in Medication Math — When to round, how to round, and writing numbers safely.
Sources
- Pharmacology for Nurses — 2.4 Dosage Calculations — OpenStax
- Nursing Skills — Math Calculations — Open RN / NCBI Bookshelf
Explanations are original Dosage Calcs wording. See all sources and the methodology.
Educational Use & Safety
Educational content only. These lessons teach medication math using fictional values and do not determine an appropriate medication, dose, infusion rate, or treatment for an actual patient.
Educational Use & Safety