Months Between Dates Calculator — Exact Month Difference
Enter a start and end date to find the exact number of complete months between them, broken down into years, remaining months and leftover days.
2 yr 6 mo 4 days remaining
- 1
Year difference in months
(2026 − 2024) × 12 = 24 - 2
Add month difference
24 + (7 − 1) = 30
How does this calculator work?
Full months = (endYear − startYear) × 12 + (endMonth − startMonth), minus 1 if the end day is before the start day (with leftover days measured against the actual month length). Total days uses timestamp arithmetic; approximate months = total days ÷ 30.4375.
Formula
How this is calculated
The calculator counts complete calendar months using year-and-month arithmetic: it computes (endYear − startYear) × 12 + (endMonth − startMonth) to get a first estimate, then checks whether the end day is before the start day. If so, the final month is not complete and one month is subtracted; the remaining days are measured against the actual length of the preceding month (28–31 days, handling leap years correctly).
The total-days figure is derived independently from Unix timestamps — milliseconds between the two dates divided by 86,400,000 — so it is exact regardless of daylight-saving transitions. Total weeks divides total days by 7 to give a decimal week count. The approximate months figure (total days ÷ 30.4375, which is the average Gregorian calendar month length) is useful for quick comparisons but will differ slightly from the complete-months count for the same reason that months are unequal in length.
The typical use cases are tracking subscription periods, pregnancy milestones, project timelines, loan tenures and age in months for infants or toddlers.
Frequently asked questions
Calendar months are 28–31 days long, not exactly 30. The complete-month count uses actual calendar boundaries, so two dates on the same day number in different months are always exactly one complete month apart, regardless of whether that month had 28 or 31 days. Dividing total days by 30 or 30.4375 gives an average approximation that will differ by up to a few decimal places.
Pregnancy is often tracked in weeks, but the number of complete calendar months from the last menstrual period is also used. Enter the LMP date as the start and today (or the due date) as the end to see the month count alongside weeks and days.
Yes. The day-borrowing step uses the JavaScript Date object to find the actual number of days in the preceding month, which is 29 for February in a leap year. Total calendar days is also computed via timestamps, which are leap-year-aware.
Also known as
TG we-Calculate Editorial Team. (2026). Months Between Dates Calculator — Exact Month Difference [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/months-between-dates-calculator
TG we-Calculate Editorial Team. "Months Between Dates Calculator — Exact Month Difference." TG we-Calculate. 2026. https://we-calculate.com/calculator/months-between-dates-calculator.
TG we-Calculate Editorial Team, "Months Between Dates Calculator — Exact Month Difference," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/months-between-dates-calculator
@misc{wecalculate_months_between_dates_calculator, title = {Months Between Dates Calculator — Exact Month Difference}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/months-between-dates-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?