How to use this calculator
- Enter or choose date filled (first dose).
- Enter or choose days supply.
- Enter or choose refill allowed after.
- The earliest refill date updates as you type. Use Copy result or Share to keep it.
Method
Last day covered = Fill date + Days supply − 1; Runs out = Fill date + Days supply; Earliest refill = Fill date + ⌈Days supply × Refill% ÷ 100⌉
- 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
- Last day covered = 29 Oct + 29 days = 27 Nov 2026.
- 75% of 30 days = 22.5, rounded up to 23 days.
- Earliest refill = 29 Oct + 23 days = 21 Nov 2026.
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.
Please note: This is a general screening estimate for adults, not medical advice or a diagnosis. Talk to a qualified health professional about your health.