What this calculator does
This calculator answers how many months between two dates, counting whole calendar months forward from the earlier date to the later one, with whatever days are left over shown separately. It also gives the same span as a single decimal number of months, for when a fractional figure is more useful than a broken-down count.
Months are not a fixed length, unlike days or weeks, so "months between two dates" can be answered a couple of different ways. Counting whole months forward from the start date (the approach used here) matches how people actually think about it: from 15 March to 15 June is exactly 3 months, regardless of how many days those particular months happened to contain.
The formula
Whole months are counted forward from the earlier date, incrementing month by month until the later date is reached, with any remaining days after the last whole month shown alongside. The decimal figure instead divides the total number of days between the dates by 30.4368, the average length of a month over a 400-year calendar cycle.
| Term | Meaning |
|---|---|
| Whole months | The number of complete calendar months counted forward from the earlier date to the later one. |
| Remaining days | Whatever is left over after the last whole month, counted forward from that point to the later date. |
| Decimal months | The total number of days between the dates divided by the average month length, 30.4368 days. |
The inputs explained
| Field | What to enter |
|---|---|
| First date | The earlier of the two dates. If the dates are entered in either order, they are automatically calculated forward in time. |
| Second date | The later of the two dates. |
When to use it
Working out a contract or lease term
Agreements are often quoted in months rather than days, so converting a start and end date into a whole-months-and-days figure matches how the term is actually described.
Tracking a pregnancy, treatment or recovery in months
Clinical and personal milestones are commonly discussed in months rather than days, and a whole-months-plus-days figure is easier to relate to a specific stage than a raw day count.
Billing or reporting on a monthly cycle
Prorating a fee or reporting a duration against monthly billing periods is more direct with a months-and-days figure than converting everything to days first.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How many months between two dates, at a fixed start date
A fixed start date of 1 January, against a range of end dates.
| End date | Whole months and remaining days | Months as a decimal | Total days between the dates |
|---|---|---|---|
| 2026-02-01 | 1 months, 0 days | 1.02 | 31 |
| 2026-04-01 | 3 months, 0 days | 2.96 | 90 |
| 2026-07-01 | 6 months, 0 days | 5.95 | 181 |
| 2026-10-01 | 9 months, 0 days | 8.97 | 273 |
| 2027-01-01 | 12 months, 0 days | 11.99 | 365 |
| 2027-07-01 | 18 months, 0 days | 17.94 | 546 |
Questions
How many months between two dates is this calculator counting?
It counts whole calendar months forward from the earlier date to the later one, the same way you would count on a calendar: 15 March to 15 June is 3 months. Anything left over after the last whole month is shown as remaining days.
Why does the decimal months figure not match the whole months exactly?
The decimal figure divides total days by 30.4368, the average month length across a 400-year cycle. Because actual months vary from 28 to 31 days, a specific pair of dates can land slightly above or below the whole-month count once converted to a decimal.
What is the difference between this and a day calculator between two dates?
A day calculator between two dates gives a single count of days, which is exact but does not translate directly into a monthly figure. This calculator is built specifically to headline the months, with days only shown as the leftover remainder or as a decimal.
Does it matter which date I enter first?
No. Enter the two dates in either order and the calculator works out which is earlier and counts forward from there, noting when it has reversed your input to do so.
For a fuller breakdown that also includes years and weeks, see the time between dates calculator. For a simple day count between two dates instead of months, use the days calculator.