Use these nursing scenarios to sanity-check the formula, then load the same values back into the calculator with one click.
Adult Tablets
A provider orders 500 mg by mouth and the stock bottle contains 250 mg per tablet.
This is the standard bedside tablet-calculation pattern used in med-surg and outpatient practice.
Pediatric Dose
A pediatric order calls for 375 mg and the available tablet strength is 250 mg.
If the tablet is not scored or the fraction is impractical, confirm an alternative strength or formulation with pharmacy.
Unit Conversion
The prescribed dose is written in grams but the stock strength is labeled in milligrams.
Converting the order and stock to the same unit before dividing is the key safety step.
The standard nursing formula for calculating the number of tablets or capsules to administer. D is the desired dose, H is the available dose per tablet, and Q is the quantity (usually 1 tablet).
X (tablets) = (D / H) × Q
Enter the desired dose ordered by the prescriber, the strength available per tablet or capsule, and the quantity (usually 1). The calculator divides D by H, multiplies by Q, and returns the number of tablets to administer. Units are automatically converted if D and H differ.
A provider orders 500 mg of amoxicillin. The pharmacy supplies 250 mg capsules. How many capsules should the nurse administer?
If the answer is not a practical whole or half tablet, pause and confirm the formulation with pharmacy before giving the medication.
The D/H × Q formula works for all solid oral dosage forms — tablets, capsules, and scored tablets that can be split. When D and H are in different units (e.g., mg vs g), convert them to the same unit first. This calculator handles that conversion automatically.
Fractional results (like 0.5 or 1.5) are common. Half-tablet doses are acceptable for scored tablets. If the result is an unusual fraction (e.g., 0.37), recheck your calculation and the original order.
Grains are part of the apothecary system and are less common today. You may encounter them with aspirin (5 gr = 324 mg) or thyroid medications. This calculator converts grains to milligrams automatically using 1 gr = 64.8 mg.
Q represents how many tablets or capsules contain the "Have" dose. In nearly all cases, Q = 1 (one tablet contains the labeled strength). Q might be greater than 1 if the pharmacy labels a dose as "per 2 tablets."
The standard nursing formula is X = (D / H) × Q. D is the desired dose, H is the dose available on hand, and Q is the quantity that contains H. The answer X is the number of tablets or capsules to administer.
Yes. Desired dose and available dose must be in the same unit before you divide them. For example, if the order is in grams and the stock strength is in milligrams, convert one so both values match first.
Pause when the answer is unexpectedly high, unexpectedly tiny, or requires an impractical tablet fraction. You should also question the result if the tablet is not scored, if the medication is extended-release, or if the calculated dose exceeds typical single-dose ranges.
Reference:
Hughes RG, Blegen MA. Medication administration safety. In: Hughes RG, ed. Patient Safety and Quality: An Evidence-Based Handbook for Nurses. Agency for Healthcare Research and Quality; 2008. https://www.ncbi.nlm.nih.gov/books/NBK2656/