When is my next refill?
Type the date your prescription was last filled and its days’ supply. The refill calculator shows the earliest day a refill is due under your plan’s rule, usually 75%, and the day the supply runs out. This is a date guide, not medical or insurance advice.
- Earliest refill date
- Monday, October 5, 2026
Filled on September 12, 2026 with 30 days’ supply, the earliest refill is Monday, October 5, 2026; the supply runs out on Monday, October 12, 2026.
- Refill
- Refill due in 3 days
- Days from fill to refill
- 23
- Supply runs out
- Monday, October 12, 2026
- Days of supply left
- 10
- Days’ supply
- 30
Answer for the example date Friday, October 2, 2026. It changes to today's date when the page loads.
Earliest refill date: Monday, October 5, 2026. Filled on September 12, 2026 with 30 days’ supply, the earliest refill is Monday, October 5, 2026; the supply runs out on Monday, October 12, 2026.
How to calculate
Finds the earliest date a pharmacy can refill a prescription, once 75% (or another share) of the days’ supply has passed, and the day the supply runs out.
Example with the default inputs (Date last filled September 12, 2026, Supply given as Days’ supply, Days’ supply 30, Share of the supply to use first 75%, Count from October 2, 2026) on the example date Friday, October 2, 2026: Filled on September 12, 2026 with 30 days’ supply, the earliest refill is Monday, October 5, 2026; the supply runs out on Monday, October 12, 2026.
Method: Days to wait = ⌈days’ supply × share ÷ 100⌉; earliest refill = date filled + days to wait; supply runs out = date filled + days’ supply.
- Plans set the share; Colorado Medicaid, for example, uses 75% of the days’ supply, and 85% for controlled drugs. Check your own plan.
- Days are calendar days; the fill date is day 0.
- From pills and a daily dose, the days’ supply is the whole days the pills last (pills ÷ pills per day, rounded down).
- This is a date guide, not medical or insurance advice; the pharmacy and the plan decide.
Worked examples
Each example is checked against the calculator on every build.
- Date last filled 2026-09-01, Supply given as Days’ supply, Days’ supply 30, Share of the supply to use first 75%, Count from 2026-09-10 gives Days from fill to refill 23, Earliest refill date 2026-09-24, Refill Refill due in 14 days, Supply runs out 2026-10-01, Days of supply left 21, Days’ supply 30.Source: Colorado Department of Health Care Policy and Financing, Pharmacy Billing Manual (refill too soon: 75% of the days’ supply for non-scheduled drugs, 85% for Schedule II to V), https://hcpf.colorado.gov/pharmacy-billing-manual, retrieved 2026-10-02
- Date last filled 2026-01-15, Supply given as Days’ supply, Days’ supply 90, Share of the supply to use first 85%, Count from 2026-04-20 gives Days from fill to refill 77, Earliest refill date 2026-04-02, Refill Refill due now, Supply runs out 2026-04-15, Days of supply left 0.Source: Colorado Department of Health Care Policy and Financing, Pharmacy Billing Manual (refill too soon: 75% of the days’ supply for non-scheduled drugs, 85% for Schedule II to V), https://hcpf.colorado.gov/pharmacy-billing-manual, retrieved 2026-10-02
- Date last filled 2026-02-20, Supply given as Pills and dose, Pills (or doses) dispensed 45, Pills (or doses) per day 2, Share of the supply to use first 80%, Count from 2026-02-20 gives Days’ supply 22, Days from fill to refill 18, Earliest refill date 2026-03-10, Supply runs out 2026-03-14.
- Date last filled 2028-02-01, Supply given as Days’ supply, Days’ supply 30, Share of the supply to use first 100%, Count from 2028-02-29 gives Earliest refill date 2028-03-02, Refill Refill due in 2 days.
How it works
With F the date last filled, S the days’ supply, and p the share (in percent) of the supply to use before a refill:
- Days from fill to refill: W = ⌈S × p ÷ 100⌉, worked exactly from the percent as typed (75 is exactly 0.75), so 30 × 75% = 22.5 rounds up to 23.
- Earliest refill date: F + W calendar days.
- Supply runs out: F + S calendar days, the first day with no medicine left.
The fill date is day 0. Days are calendar days in the Gregorian calendar, leap days included.
With Pills and dose, S = ⌊pills ÷ pills per day⌋, the whole days the pills last, worked exactly from the numbers typed (3 pills at 0.1 a day is 30 days). When the pills last less than one day there is no answer: "The pills last less than one day at this dose." When they last more than 1,000 days: "The pills last more than 1,000 days at this dose."
From the count-from date C (today, unless you change it):
- Refill: with D = days from C to the earliest refill date,
Refill due nowwhen D is 0 or less,Refill due in 1 daywhen D is 1, andRefill due in D daysotherwise. - Days of supply left: the days from C to the run-out date, or 0 once it has passed.
Limits: days’ supply 1 to 1,000; pills 1 to 100,000; pills per day 0.01 to 1,000; share 0% to 100%; dates from 1900 to 2400.
Plans differ. Colorado Medicaid, for example, uses 75% for non-scheduled drugs and 85% for DEA Schedule II to V drugs. Check with your pharmacy or plan.
Worked examples by hand
30 days filled September 1, 2026, at 75%, counting from September 10. 30 × 0.75 = 22.5, so 23 days; September 1 + 23 = September 24, 2026, which is 14 days after September 10. The supply runs out on September 1 + 30 = October 1, 2026, 21 days after September 10.
90 days filled January 15, 2026, at 85%, counting from April 20. 90 × 0.85 = 76.5, so 77 days; January 15 + 77 days = 16 (rest of January) + 28 + 31 = 75 days to March 31, then 2 more: April 2, 2026. That is before April 20, so the refill is due now. The supply ran out on April 15, so 0 days are left.
45 pills at 2 a day, filled February 20, 2026, at 80%. 45 ÷ 2 = 22.5, so 22 days’ supply; 22 × 0.8 = 17.6, so 18 days; February 20 + 18 days = March 10, 2026 (February 2026 has 28 days). The supply runs out on February 20 + 22 = March 14.
30 days filled February 1, 2028, at 100%, counting from February 29. 2028 is a leap year, so February 1 + 30 days = March 2, 2028, 2 days after February 29.
Other questions people ask
How early can I refill a prescription?
Plans let a refill go through once a set share of the days’ supply has passed, and the share is higher for controlled drugs. Colorado Medicaid, for example, uses 75% for ordinary drugs and 85% for DEA Schedule II to V drugs. For a 30-day supply at 75%, that is day 23.
How is the refill date worked out?
Multiply the days’ supply by the share and round up to a whole day, then add that many days to the fill date. 30 × 0.75 = 22.5, which rounds up to 23, so a fill on September 1 can be refilled from September 24.
When is a 90-day prescription due for a refill?
At 75%, after ⌈90 × 0.75⌉ = 68 days; at 80%, after 72 days; at 85%, after 77 days. Add the days to the fill date.
What if I only know the number of pills?
Choose Pills and dose, and type the pills dispensed and how many you take a day. 45 pills at 2 a day last 22 whole days, which the calculator uses as the days’ supply.
What does refill too soon mean?
A pharmacy claim the plan turns down because not enough of the last fill’s days’ supply has passed. A change in dose, a lost supply, or travel may allow an override; ask your pharmacy.
When does my supply run out?
On the fill date plus the days’ supply. A 30-day fill on September 1 runs out on October 1, the first day with no medicine left if you take it as prescribed.