What this calculator does
A months calculator answers a question that days and weeks alone do not: how many whole months sit between two dates, with whatever is left over shown as a handful of remaining days. Enter a start and an end date and the result reads the way people actually talk about a span of time, such as "5 months and 27 days", rather than a raw day count that needs converting by hand.
Months are an awkward unit to count because they are not a fixed length: February runs short, and 31-day months run long. This calculator walks forward from the earlier date a whole calendar month at a time, so the answer to how many months reflects the actual calendar rather than an average month length, and a decimal figure is given alongside it for anyone who needs a single number.
The formula
Whole months are counted forward from the earlier date, one calendar month at a time, until adding one more month would overshoot the later date. Whatever days are left over after that are shown as the remainder. The same span is also given as a decimal, using an average month length of 30.4368 days, and as total days and weeks.
| Term | Meaning |
|---|---|
| Start date | The earlier date the count begins from. |
| End date | The later date the count runs to. |
| Whole months | The number of complete calendar months that fit between the two dates. |
| Remaining days | Whatever is left over after the whole months are counted, always fewer than the days in a full month. |
The inputs explained
| Field | What to enter |
|---|---|
| Start date | The earlier date. Defaults to today. |
| End date | The later date to calculate months to. |
When to use it
Calculate months for a project or contract term
A project length or a contract term stated in months needs the actual calendar to resolve to a specific end date, and this calculator shows both the whole-months figure and the exact day count behind it.
How many months pregnant, or how many months until a milestone
Plenty of "how many months" questions run forward from a known date to one that has not happened yet, and the remaining-days figure shows exactly how far into the next month that milestone falls.
Checking a months figure against a decimal quote
Some quotes or schedules state a span as a decimal number of months rather than a whole-months-and-days breakdown; the decimal figure here lines up with that style directly.
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 from today to a range of later dates
A series of later dates, each measured back to today as whole months and days, and as a decimal figure.
| End date | Whole months and days between the dates | As a decimal figure |
|---|---|---|
| today+30 | 0 months, 30 days | 0.99 months |
| today+90 | 2 months, 29 days | 2.96 months |
| today+180 | 5 months, 27 days | 5.91 months |
| today+365 | 12 months, 0 days | 11.99 months |
| today+540 | 17 months, 22 days | 17.74 months |
| today+730 | 23 months, 30 days | 23.98 months |
Questions
How many months is a set number of days?
It depends on which days those are, since months vary in length. Enter a start date and the end date that day count lands on, and the whole-months-and-days breakdown, plus the decimal figure, both come back immediately.
How do I calculate months between two dates I already know?
Enter the earlier date as the start date and the later one as the end date. If they are entered the other way round, they are swapped automatically so the count still runs forward in time.
Why is the decimal figure not a round number even for a whole number of months?
The decimal figure divides the actual day count by an average month length of 30.4368 days, since real months are not all the same length; only a span that happens to match that average exactly will land on a round decimal.
Is this the same as the date calculator?
The date calculator starts from a date and a number of months and finds the resulting date. This calculator works the other way: it starts from two known dates and finds the months and days between them.
To find the years, months and days between two dates together, see the time between dates calculator. To add or subtract a number of months from a date, use the date calculator.