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Prescription Refill Calculator

Health

Calculate how many days your remaining medication will last and when to request a refill, based on pills remaining and daily usage.

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Days of Medication Remaining

30
Request Refill In (Days)
25
Guidance
Request your refill in about 25 day(s) to allow for pharmacy processing time before your supply runs out.

This calculator computes your Days of Medication Remaining, Request Refill In (Days), Guidance from the values you enter.

Inputs
Pills/Doses RemainingDoses Taken per DayRefill Buffer
Outputs
Days of Medication RemainingRequest Refill In (Days)Guidance

What is a Refill Calculator?

The Prescription Refill Calculator is a purely administrative tool that calculates how many days your remaining medication supply will last, and suggests when to request a refill based on a buffer period you specify. It performs simple day-counting arithmetic — pills remaining divided by daily usage — with no medication-specific dosing content.

This tool helps with scheduling and planning, not with determining an appropriate dose or medication. For weight-based dosing math, see the Dosage Calculator; for scheduling multiple daily doses, see the Medicine 3 Times a Day Calculator.

How to use this Refill Calculator calculator

  1. Enter Pills/Doses Remaining — your current supply count.
  2. Enter Doses Taken per Day — your regular daily usage rate.
  3. Enter your Refill Buffer — how many days before running out you want to request a refill.
  4. Review Days of Medication Remaining and Request Refill In (Days).
  5. Read the Guidance field for your next action.

Formula & Methodology

Days Remaining = ⌊Pills Remaining ÷ Doses per Day⌋ (rounded down)

Request Refill In = max(0, Days Remaining − Refill Buffer)

Worked example — for 30 pills remaining, 1 dose per day, and a 5-day buffer:

Days Remaining = ⌊30 ÷ 1⌋ = 30 days
Request Refill In = 30 − 5 = 25 days

This is a pure scheduling calculation — always account for any additional processing time your specific pharmacy or prescription requires.

Frequently Asked Questions

It divides your pills remaining by your daily usage rate to find how many days of supply you have left, then subtracts a buffer period you specify (to allow for pharmacy processing time) to suggest when to actually request the refill.
This depends on your pharmacy's typical processing time and whether your medication requires insurance pre-authorization, mail-order shipping, or other steps that take extra time — a 5 to 7 day buffer is common for standard pharmacy pickup, but mail-order prescriptions often need a longer buffer.
No — it assumes a consistent daily usage rate. If your dose varies from day to day (for example, an as-needed medication), use your average daily usage for a rough estimate rather than an exact calculation.
Enter your daily usage as a decimal (for example, 0.5 for half a pill per day) — the calculator handles fractional daily doses the same way it handles whole numbers.
Yes — the calculation works the same way for any product taken on a regular schedule, whether it's a prescription medication, OTC product, or supplement.
Rounding down gives a more conservative (safer) estimate — it ensures the calculator doesn't overestimate how many full days of medication you actually have left.
Build extra time into your refill buffer to account for these additional steps, since this calculator only handles the basic days-remaining arithmetic and doesn't know about your specific prescription's requirements.
Use this as a planning reminder, but also account for known upcoming disruptions like holidays, travel, or pharmacy closures that might affect your usual refill timeline.
Yes — enter your pills remaining and daily usage to see how many days your current supply covers, which helps you determine whether you need to request an early refill or extra supply before a trip.
No — this is a general-purpose scheduling tool that works for any medication or supplement taken on a regular daily schedule, with no medication-specific content.
Also known as
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