Days Supply Calculator

Introduction

Estimate prescription days supply from quantity dispensed and the directions (dose × times per day). Keep quantity and dose units the same (both tablets, both mL, etc.).

Disclaimer: This tool is for informational purposes only and is not professional medical, pharmaceutical, financial, or tax advice. Always verify doses with a licensed clinician or pharmacist.

Formula

Days supply equals quantity dispensed divided by the product of dose amount and doses per day.

• Q — Quantity dispensed (tablets, mL, etc.)
• d — Amount per dose
• f — Doses per day

Step-by-step

1. Enter quantity dispensed (e.g. 30 tablets or 100 mL).
2. Enter amount taken each dose.
3. Enter how many doses are taken per day.

Worked example

30 tablets of 1 tablet twice daily last 15 days.

Use cases

• Check insurance days-supply edits
• Plan refill timing
• Verify technician days-supply calculations

Frequently asked questions