For a full bottle on the day you get it, the answer is one division: 180 tablets taken twice a day last 90 days. If that is your question, how many months is 180 tablets has tables for every common bottle size, and the tablets to months calculator does any count.
Most of the time, though, the bottle has already been opened. You don't remember exactly when you started it, and your dose may not be the same every day. Then the answer has to come from what is in the bottle now, because the number on the label no longer tells you much.
The sum, starting from today
Days left = tablets in the bottle now ÷ tablets you take per day.
Tablets per day means the total for the day: one tablet twice a day is 2, and half a tablet twice a day is 1. Two details decide whether the result is right.
Count only whole days. 47 tablets at 2 a day is 23 full days with 1 tablet over, and that spare tablet covers one dose on the 24th day, not the whole day.
Then check whether today's doses are already out of the bottle. If you count in the morning before your first dose, the 23 days start today. If you count in the evening after your last dose, today is already covered and the 23 days start tomorrow. One day is a small difference, unless you are working out when to reorder.
For example, you count 47 tablets on Monday 2 November 2026 before the morning dose, and you take one twice a day:
| Counted | First day covered | Last full day | The spare tablet |
|---|---|---|---|
| Before the morning dose | Monday 2 November | Tuesday 24 November | Morning dose on Wednesday 25 November |
| After the evening dose | Tuesday 3 November | Wednesday 25 November | Morning dose on Thursday 26 November |
The refill date calculator does this from any date, and also gives you a day to order by.
When the dose is not the same every day
Find the pattern that repeats, often a week, and add up the tablets in one round of it. Divide the bottle by that total, then walk through the leftover tablets day by day.
| Schedule | Tablets per round | Counting from | 60 tablets: last full dose |
|---|---|---|---|
| 1 on weekdays, 2 at weekends | 9 a week | a Monday | day 47 (a Friday), 1 tablet over |
| 1 a day, none on Sundays | 6 a week | a Monday | day 69 (a Saturday) |
| 1 and 2 on alternate days | 3 every 2 days | either dose | day 40 |
| 1 every other day | 1 every 2 days | the first dose | day 119 |
| 1 a day, 3 weeks on, 1 week off | 21 every 4 weeks | the first day of an on week | day 74 |
Where the leftover tablets land depends on the day you start counting. Take the first row: 60 tablets make 6 full weeks with 6 tablets over. Counted from a Monday, those 6 cover Monday to Friday and leave 1, which is not enough for Saturday's 2, so that is 47 days. Counted from a Saturday, the same 6 cover Saturday, Sunday, Monday and Tuesday, so you get 46.
Every other day has its own write-up, every other day medication schedules, and on-and-off cycles can be turned into dates with the medication cycle calculator. A taper is the far end of this: the dose changes every few days, so add up each step's tablets until you reach what you have. The taper schedule calculator gives you the date each step starts and ends.
Two strengths making up one dose
Sometimes one dose is made from two different tablets, for example 15 mg taken as one 10 mg tablet and one 5 mg tablet. Each bottle runs out on its own schedule, so work them out separately. The smaller number is the day you can no longer make up the full dose.
With 40 of the 10 mg tablets and 25 of the 5 mg tablets, once a day, the 5 mg bottle runs out after 25 days while 15 of the 10 mg tablets are still left. Order by the bottle that runs out first. If one strength does run out, ask your pharmacist before you make up the dose any other way.
Two bottles of the same strength, such as an old one and a new one, are simpler. Add them together, then divide.
As-needed medication
A medicine you take only when you need it has no fixed tablets per day, so there are two useful numbers.
- The shortest it can last: divide by the most you are allowed in a day, from the label. 24 tablets with a maximum of 4 a day last at least 6 days.
- How long it will probably last: use your own recent rate. If you took 7 in the last 14 days, that is half a tablet a day, so 24 tablets last about 48 days at that pace.
Every 4 hours as needed explains how the minimum gap and the label's daily maximum limit as-needed doses.
Turning days into a reorder date
Order well before the bottle runs out. The pharmacy needs time to fill it, and a weekend or a late delivery can add days. Your insurance also decides how early you are allowed to refill. Most plans want most of the last supply used first, and refill too soon explains the percentages.
If you started from a known count and the bottle looks fuller or emptier than it should, the pill count checker shows how many should be left today and what the gap means. Either way, work from the count in your hand. It is the one number that already includes every missed, dropped or extra dose.
Let the count keep itself
The arithmetic is easy to do once. Redoing it after every dose and every new bottle is the tedious part, especially with several medicines that run out on different days.
Doz keeps that count for you. Enter how many tablets are in the bottle once, and it takes the dose off each time you log it. When the count drops to a number you choose, the medication is flagged as low in the app while there are still tablets left. When the new bottle arrives, add it to the count and the figure stays accurate.
Doz is a free download on the App Store: a running pill count, low-stock warnings before you run out, and no account to create.
Frequently Asked Questions
How long will my pills last?
Divide the tablets in the bottle now by the number you take per day, and count only whole days. 47 tablets at two a day is 23 full days with one tablet over. For a full new bottle, 180 tablets twice a day last 90 days.
Should I count today's dose?
If you count before taking today's doses, today is the first day covered. If you count after, today's doses are already out of the bottle, so start from tomorrow.
How do I work it out if my dose changes during the week?
Add up the tablets in one week, or in whatever pattern repeats, and divide the bottle by that total. One tablet on weekdays and two at weekends is 9 a week, so 60 tablets cover 6 full weeks with 6 tablets over.
How long do as-needed pills last?
Divide by the maximum you are allowed per day to get the shortest the bottle can last. For a realistic figure, use how many you actually took over the last couple of weeks.
The short version
Count what is in the bottle today and divide by what you take per day. Count only whole days, and decide whether today's doses are already out. If the dose changes, use the pattern that repeats. If two strengths make one dose, the bottle that runs out first sets the date. Then turn the result into a date and reorder well before it.
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