Prescription refill calculator

Enter what is actually in the bottle. The calculator works out the day your supply runs out, and the earlier day you should order by so you never get down to the last two pills on a weekend.

What to do with the number

The order-by date is the useful one. The run-out date tells you when you have a problem; the order-by date tells you when to act so you never have one.

Two things worth checking the moment you hit that date. First, whether the prescription has repeats left, or whether you need a new one — that is the step with a queue in front of it. Second, whether a review appointment is required, because appointments are booked weeks out and pills are not.

There is a longer write-up of the whole system in four ways to know you're running low, including the version that works with a pen and the bottle label. If you would rather not keep the count by hand, Doz tracks stock per medication and warns you at a pill threshold you set, rather than at a date that drifts.

Working from a fill date instead of a pill count? The days supply calculator turns a quantity into days, and the refill too soon calculator shows the earliest date your plan is likely to pay for the next fill. For an as-needed medication, enter the number you typically take in a day; the dates are only as good as that average.

Common questions

How many days of buffer should I leave?

Around seven days for a once-daily medication. That covers a weekend, a public holiday, and a pharmacy that has to order your medication in. If a refill needs a prescription renewal or a review appointment, leave considerably more — that step can take weeks.

Why calculate by pill count instead of by date?

A fixed refill date drifts the moment you skip a dose or take an extra one, and nothing tells you that it drifted. A pill count is tied to what is physically in the bottle, so it stays accurate.

Does having pills left mean I can get a refill?

No. Some prescriptions have a limited number of repeats before you need a new one, and some need a review appointment first. The pill count tells you about supply, not about access, so when you hit your threshold check how many steps are between you and the next box.

How do I work out a refill date for a 28, 30 or 90-day supply?

Count the day you start as day one, so the supply covers the start date plus one day fewer than its length. A 90-day supply of one tablet a day started on 1 October 2026 lasts until 29 December 2026; with a seven-day buffer you would order by 22 December. A 28-day pack started the same day lasts until 28 October. Because 28-day packs are shorter than a calendar month, your refill date moves two or three days earlier in most months, and a year takes about 13 packs rather than 12.

Can I refill as soon as I reach the order-by date?

Ordering and being allowed to refill are different things. Many insurance plans will not pay for a refill until you have used most of the last one, often 75 to 85 percent of the days supply. If your order-by date comes before that point, the refill too soon calculator shows the earliest date the plan is likely to accept.

One thing this cannot do

This is an arithmetic tool, not medical advice. It works out dates and times from numbers you type in — it does not know your medication, your prescription, or what you should do if something goes wrong. Anything about changing a dose, spacing doses differently, or handling a missed dose is a question for your doctor or pharmacist.