Tablet Dosage Calculator (D/H × Q)
Convert a prescribed dose to the number of tablets or capsules using the classic Desired ÷ Have × Quantity formula.
Understanding this tool
Why nurses use it
Nurses use tablet dosage math daily when the prescribed dose does not match the stock strength on the ward — for example, an order for 500 mg when only 250 mg tablets are available. The Desired ÷ Have × Quantity (D/H × Q) method is the standard nursing approach taught in medication safety training and NCLEX-style questions.
When to use it
Use when administering solid oral medications (tablets or capsules) and you need to convert a prescribed milligram dose into a number of units to give. Always cross-check with the medicine label, the eMAR, and your local double-check policy before administration.
Calculate
How to use this calculator
- Confirm the prescribed dose (Desired) in mg from the order or eMAR.
- Read the strength on the stock label (Have) — mg per tablet or capsule.
- Enter Quantity as 1 unless your protocol uses a different quantity factor.
- Calculate, then round to a practical number of tablets per local policy.
- Complete independent double-check for high-risk medicines.
How the calculation works
The formula Tablets = (Desired dose ÷ Have on hand) × Quantity tells you how many stock units contain the ordered dose. If Desired and Have share the same unit (mg), dividing gives the proportion of one tablet needed; multiplying by Quantity adjusts when the formula is scaled differently.
Formula used by this tool — verify units before applying at the bedside.
Worked example
Limitations & clinical notes
- Does not replace pharmacy verification or controlled-drug double-checks.
- Round to practical tablet fractions per local policy.
References
Key sources: NICE — Medicines optimisation.
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Disclaimer: This calculator is for educational and bedside double-check purposes only. It does not replace institutional protocols, prescriber orders, pharmacist verification, or clinical judgment. Always follow your local policies — especially for high-risk medications, infusions, pediatrics, and critical care. If the patient is acutely unwell, escalate immediately rather than relying on any calculator output.