Medication refill calculator: days left, run-out date, and refill timing
Use this medication refill calculator to estimate how many days of supply you have left, your likely run-out date, and when to request a refill from the pharmacy.
Calculate days left and when to request a refill
Enter your remaining supply and routine. The calculator estimates your run-out date, refill request date, and reminder window.
Your estimated refill window
On trackHow this estimate works: We divide your current supply by your daily use, then move the refill date earlier based on your pharmacy lead time and safety buffer.
Keep refill planning inside the app
MyMedAlert can remind you before your supply gets low so you do not have to calculate this manually every month.
Why this calculator helps
Good refill planning comes down to three things: how much medication you have left, how fast you use it, and how early you need to act. The calculator turns those inputs into dates you can use for a refill reminder, a pharmacy call, or a note before your next request.
It is built for quick routine planning. You do not need an old receipt or spreadsheet; start with the supply in front of you and add enough buffer for real-world delays like weekends, prescriber callbacks, prior authorization, or stock issues.
How to use the refill calculator
Start with the amount you can actually use today. Count tablets, capsules, injections, patches, or doses that are not expired and that still match the label from the pharmacy. Then enter how much you take at one time and how many times you take it in a normal day.
Use the pharmacy lead time for the way you usually refill. A local pharmacy may need only a few days. Mail order, prior authorization, holidays, or stock shortages can take longer. The safety buffer is the extra time you want before the bottle is empty.
Formula and date logic
The calculator uses simple supply math:
| Step | Method |
|---|---|
| Daily use | amount per dose x doses per day |
| Supply left | current supply / daily use |
| Request date | estimated empty date minus pharmacy lead time |
| Reminder date | request date minus safety buffer |
The result is a planning estimate. It does not check insurance refill rules, controlled-substance limits, prescription expiration, dose changes, or whether a pharmacy has the medicine in stock.
Example
If you have 30 tablets left, take 1 tablet twice a day, and your pharmacy usually needs 5 days, you have about 15 days of supply. With a 3 day buffer, the reminder date is about 7 days before the bottle is empty. That gives you time to request the refill, answer pharmacy questions, and avoid a missed dose.
What can change the result
- A prescriber changes the dose or frequency.
- You split tablets, use half doses, or take an extra dose by instruction.
- You miss doses and do not update the count.
- A refill needs a new prescription or prior authorization.
- Mail delivery, weekends, holidays, or travel add extra days.
Recalculate whenever the dose changes or after you refill. For medicines you take every day, setting the reminder before you feel close to running out is usually safer than waiting for the last few doses.
When to ask the pharmacy or prescriber
Ask a pharmacist or prescriber if the directions are confusing, if the pill looks different after a refill, if you are not sure what to do after a missed dose, or if you are taking prescription medicines together with over-the-counter medicines, vitamins, or supplements. Do not stop or change a prescribed medicine just because the date estimate looks inconvenient.
Related tool
If the refill date is only one part of the routine, build a printable weekly plan with the medication schedule builder.
You can also compare this with other free medication tools, including planners for schedules, half-life estimates, supplements, hydration, and blood sugar conversion.
Common questions about refill timing
How does the refill calculator work?
It divides your current supply by how many pills or doses you use each day, then works backward from the estimated run-out date using your pharmacy lead time and safety buffer.
What if I take half tablets or multiple pills per dose?
Enter the exact amount you take per dose. For example, use 0.5 for half a tablet or 2 if you take two capsules each time.
Is this tool a substitute for medical advice?
No. It is a planning aid only. Always confirm refill timing and dosage instructions with your pharmacist or prescriber.