Step 1: Convert inputs to common units.
Step 2: Solve equation.
X = (D / H) × Q
X = (500 / 250) × 1
Result = 2 tablet(s)
The oral dosage formula X = (D / H) × Q is the standard method nurses use to determine how many tablets or capsules to administer for a given medication order.
A provider orders 500 mg of amoxicillin. The pharmacy supplies 250 mg capsules. How many capsules should the nurse administer?
X = (500 mg / 250 mg) × 1 = 2 capsules
This calculator automatically converts between units when the desired dose and available dose use different measurement systems.
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."