Prescription Refill Calculator

To perform 30 day prescription refill calculations, divide the total quantity dispensed by the daily dose and verify the result equals 30 days. For a 30 day supply of a once-daily medication, the pharmacy dispenses 30 tablets. For a twice-daily medication, the pharmacy dispenses 60 tablets (60 ÷ 2 = 30 days). Most insurance plans allow a refill when 75% of the 30 day supply has been used—around day 22 to 25. Enter your quantities in the calculator above to get the exact date for a 30 day prescription.

To perform 90 day prescription refill calculations, divide the total quantity dispensed by the daily dose and confirm the result equals 90 days. A 90 day supply of a once-daily medication requires 90 tablets. A twice-daily medication requires 180 tablets (180 ÷ 2 = 90 days). Mail-order pharmacies commonly dispense 90 day supplies to reduce cost per unit and pharmacy visits. Insurance plans typically allow a 90 day refill around day 80 to 83. Use the calculator with 90 tablets and 1 per day to see the exact 90 day prescription refill date.

To perform 28 day prescription refill calculations, divide the total quantity dispensed by the daily dose and confirm the result equals 28 days. Controlled substance prescriptions (Schedule II medications like Adderall and Oxycodone) use 28 day cycles instead of 30 day cycles. A once-daily controlled substance prescription dispenses 28 tablets with a refill eligibility date 28 days from the fill date. This tool computes 28 day supply schedules—enter 28 for total pills and 1 per day to see your controlled substance refill date.

A refill calculator is a digital health tool that estimates when a medication supply will run out based on quantity dispensed and daily dosage. This tool takes 3 core inputs—total pills, pills per day, and fill date—and returns the exact date the supply reaches zero. Patients use refill calculators for medication adherence, pharmacy planning, and avoiding gaps in treatment. Healthcare providers and pharmacies use day supply calculations for insurance billing, inventory management, and refill authorization.

No, all calculations run in your web browser. This tool does not collect, store, or transmit medication information to any server. No account registration is required, and no cookies track your prescription data.

Yes, enter the total number of pills taken per day in the "Pills Per Day" field. Take 1 tablet in the morning and 1 tablet at night—enter "2" as the daily dose. The medication refill calculator accepts fractional doses like 0.5 for half-tablet dosages.

The recommended refill-by date is set 3 to 5 days before the supply runs out. This buffer accounts for 3 common delays: pharmacy processing time (1 to 2 business days), insurance prior authorization reviews (1 to 3 business days), and weekends or holidays when pharmacies may be closed. Refilling 3 to 5 days early avoids gaps in medication adherence.

Yes, this tool is 100% free with no registration, no subscription, and no limits. Use it for any number of medications, as many times as needed. The calculator works on all devices—desktop, tablet, and mobile browsers.