# Prescription Refill Date Calculator

> Find the last day a prescription covers, the day it runs out and the earliest refill date when your plan allows a refill after a set share of the supply is used.

Category: Healthcare operations · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/prescription-refill-date-calculator

Starting on the fill date, the supply covers as many days as its days supply. Many plans allow a refill once a set percentage of those days has passed; enter your plan’s figure.

Also called: Refill too soon calculator.

## Inputs
- Date filled (first dose) (default 2026-10-29)
- Days supply (unit days; default 30)
- Refill allowed after (unit % used; default 75)

## Results
- Earliest refill date
- Last day covered
- First day without medicine
- Days after filling

## Formula

```
Last day covered = Fill date + Days supply − 1;  Runs out = Fill date + Days supply;  Earliest refill = Fill date + ⌈Days supply × Refill% ÷ 100⌉
```

Where:
- Fill date: day the supply starts (first dose)
- Days supply: days the dispensed quantity lasts
- Refill%: share of the supply your plan requires to be used first

## Worked example
1. Last day covered = 29 Oct + 29 days = 27 Nov 2026.
2. 75% of 30 days = 22.5, rounded up to 23 days.
3. Earliest refill = 29 Oct + 23 days = 21 Nov 2026.

**Result:** A 30-day supply filled on 29 October 2026 lasts to 27 November; at a 75% rule the refill can be requested from 21 November.

## What the result means

Request the refill between the earliest refill date and the last day covered, allowing for delivery or pharmacy opening hours. If doses are missed, the supply will last longer than shown.

## Assumptions and limits
- The first dose is taken on the fill date and directions are followed every day.
- The refill threshold is the percentage you enter; no plan rule is built in.
- Controlled medicines, mail-order and vacation supplies often have different rules.
- Partial days are rounded up to whole days for the refill date.

## Questions

### Why can’t I refill whenever I want?

Insurers and pharmacies limit early refills to prevent stockpiling and waste. The allowed point is usually a percentage of the days supply.

### How do I find the days supply?

It is printed on many labels and receipts, or work it out with the days supply calculator from the quantity and directions.

## Related calculators
- [Medication Days Supply Calculator](https://calculators.geekmidst.com/calculators/medication-days-supply-calculator)
- [Date Calculator](https://calculators.geekmidst.com/calculators/date-calculator)
- [Date Difference Calculator](https://calculators.geekmidst.com/calculators/date-difference-calculator)

_This is a general screening estimate for adults, not medical advice or a diagnosis. Talk to a qualified health professional about your health._

Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/prescription-refill-date-calculator