Pharmacy Days Supply Calculator by Dosage Form

Calculation mode

Use a product preset (optional)

Optional exact-product preset

Presets fill only exact label or package facts. All prescription-specific inputs remain yours to verify.

Rounding and source note (optional)

Optional explicit rounding

Source or convention note (optional; do not include PHI)

Do not enter patient identifiers, prescription numbers, or other PHI. A payer or plan may require a different convention.

JavaScript is required for this calculator. Use the days supply formulas and worked examples to calculate manually.

Before using the result

Verify the prescription inputs. Product presets fill only cited label or package facts; they do not fill the dose, frequency, treatment area, or concurrent patch count.
Keep the unrounded result. Select round up or round down only when the current payer or system rule supports that choice.
Check limiting instructions. Treatment duration, in-use discard dates, priming, usable counts, and package limits can shorten or change a purely quantity-based result.
Do not infer missing clinical information. Clarify an unusable PRN maximum, sliding scale, taper, treatment area, or other ambiguous direction.

Quantity dispensed ÷ supported maximum daily use.

(Bottle mL × an explicit drops-per-mL convention) ÷ drops used per day.

Labeled usable count ÷ maximum inhalations or sprays used per day.

Complete injections per pen, divided by injections per day, limited by each pen’s in-use period; multiply by identical pens used sequentially.

(Patch count ÷ concurrent patches) × wear interval.

Direct grams per application, CMS's 2015 Rule of Hand, or an explicit adult FTU estimate.

The NCPDP days-supply discussion describes quantity-based estimates and rounding considerations. The CMS 2015 dosage-form job aid supplies historical estimation examples, not a universal current payer rule.

Sources8 linked sources