Calculate when to refill your prescription based on pill count, dosing frequency, and lead time. Plan ahead to never run out of medication.
Missing a medication dose due to an empty prescription can disrupt treatment effectiveness and pose health risks, especially for chronic conditions requiring consistent dosing. This prescription refill calculator helps you determine exactly when you'll need to request your next refill based on your current supply, dosing schedule, and pharmacy lead time.
The calculator supports all common dosing frequencies — from once daily to every 4 hours, as well as weekly and monthly medications. It computes your daily pill consumption rate, total days of supply remaining, the date you'll run out, and the optimal date to call your pharmacy for a refill accounting for processing time.
For ongoing medications, the calculator projects a full 6-refill schedule, showing you exactly when each future refill should be requested. This is particularly valuable for 90-day mail-order prescriptions, controlled substances that cannot be filled early, and medications that require prior authorization renewals. Check the example with realistic values before reporting.
Running out of chronic medication is a common problem that can lead to missed doses, disease flare-ups, and emergency healthcare visits. This calculator takes the guesswork out of refill timing by computing exact dates based on your dosing schedule. It's especially valuable for patients taking multiple medications, those using mail-order pharmacies with longer lead times, and caregivers managing medications for family members.
Pills Per Day = Doses Per Intake × Intakes Per Day Days Supply = Remaining Pills ÷ Pills Per Day Run-Out Date = Start Date + Days Supply Refill Date = Run-Out Date − Lead Time Days
Result: 90 days supply, run out June 6, refill by May 30
Taking 1 pill daily from a 90-count bottle gives 90 days of supply. Starting March 8, the supply runs out June 6. With a 7-day lead time for pharmacy processing, the refill should be requested by May 30.
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Most pharmacies allow refills when 75–80% of the supply has been used (typically 7–10 days before running out for a 30-day supply). Controlled substances (Schedule II-V) often have stricter rules — typically no earlier than 2–3 days before the supply runs out.
Retail pharmacies usually fill prescriptions within 1–2 days. Mail-order pharmacies need 7–14 days including shipping. Specialty medications may require 10–14 days due to prior authorization or specialty sourcing.
Yes. If you skip doses, your actual supply will last longer than calculated. Update the "pills remaining" field periodically to keep the calculator accurate. Consistent timing matters most for medication effectiveness.
Many insurance plans offer 90-day supplies (often through mail order) at a lower copay per pill. You'll refill approximately 4 times per year instead of 12, which is more convenient for stable, chronic medications.
Doctors can write prescriptions with multiple refills (e.g., "1 year with 11 refills" for a 30-day supply). However, controlled substances may require a new prescription each time. Ask your pharmacy about auto-refill programs.
Days supply is the number of days the prescription should last at the prescribed dose. Insurance companies use this to determine when you're eligible for a refill. It's calculated the same way as this calculator — total quantity divided by daily usage.