How to Calculate Months Between Two Dates

To calculate the months between two dates, open the Month Calculator, set Calculate to "Months between dates," enter a Start date and End date, and read the Months total — along with an exact breakdown into months and days, years/months/days, and total days.

What the Month Calculator does

"How many months is that?" is harder to answer by hand than it looks, because months don't all have the same number of days. The Month Calculator handles two related jobs: counting the calendar months (and leftover days) between two dates, or taking a single date and adding (or subtracting) a number of months to find the resulting date. Both run entirely in your browser.

How to calculate months between two dates with Toolbench

1. Open the Month Calculator.
2. Leave Calculate set to "Months between dates" (this is the default mode).
3. Enter the Start date. It defaults to today.
4. Enter the End date.
5. Read the Months figure at the top, then check the rows below for the same span as an exact "X months, Y days" count, a "years, months, days" breakdown, and the total number of days.

If the end date you enter is earlier than the start date, the tool swaps them internally so the math still works — it doesn't matter which field you put the earlier date in.

How to add or subtract months from a date

1. Open the Month Calculator.
2. Set Calculate to "Add or subtract months."
3. Enter the Start date.
4. Enter Months to add (negative to subtract) — use a negative number to go backward.
5. Read the Resulting date, plus its day of the week and the number of days between the start date and that result.

When adding months would land on a day that doesn't exist in the target month (like adding a month to January 31), the tool clamps the result to the last valid day of that month instead of rolling over into the next one.

A real worked example

With Calculate set to "Months between dates," Start date left at today (October 17, 2026) and End date set to 2027-12-31:

Metric	Result
Months	14.45
Exact	14 months, 14 days
Years, months, days	1y 2m 14d
Total days	440

That's 1 year, 2 months and 14 days — 14 full months plus 14 extra days, or 440 days total. The top-line "Months" figure (14.45) adds those 14 leftover days as a fraction of December's length (14 days ÷ 31 days in December ≈ 0.45), so it's a more precise decimal version of the same span, not a separate calculation.

Example: adding and subtracting months

Starting from January 31, 2026:

Months to add	Resulting date	Day of week	Days difference
1	February 28, 2026	Saturday	28
-1	December 31, 2025	Wednesday	-31

Adding 1 month to January 31 would land on "February 31," which doesn't exist, so the tool clamps it to February 28 (2026 isn't a leap year). Subtracting 1 month lands cleanly on December 31, 2025, since December has 31 days too.

Tips and common mistakes

• "Months" and "Exact" aren't the same number. "Months" (14.45) is a precise decimal that accounts for leftover days as a fraction of the current month's length. "Exact" (14 months, 14 days) keeps the leftover days as a separate whole number. Use whichever format fits what you're reporting.
• Short months can clamp your result. Adding months to the 29th, 30th or 31st of a month can land you on a shorter month that doesn't have that day — the tool moves the result back to that month's last day instead of spilling into the next month.
• Order doesn't matter in "Months between dates" mode. Put either date in either field; the tool sorts them before calculating.
• This counts calendar months, not an average. If you need the days between two dates converted to an approximate number of months instead, the Days Calculator uses an average month length for that; this tool always counts real calendar months.
• For add/subtract mode, a negative number means "subtract." There's no separate subtract option — type a minus sign in front of the number instead.

Related tools

• Days Calculator — days, weeks, business days and weekend days between two dates.
• Age Calculator — exact age in years, months and days from a date of birth.
• Hours Calculator — hours worked between two times, minus breaks, with pay.

Frequently asked questions

How do I calculate the number of months between two dates?

Open the Month Calculator, set Calculate to "Months between dates," and enter a Start date and End date. It returns the exact months and leftover days, a years/months/days breakdown, and the total day count.

How do I add months to a date?

Set Calculate to "Add or subtract months," enter the Start date, then enter the number of months in "Months to add." Use a negative number to subtract months instead. The tool returns the resulting date, its day of the week, and how many days separate it from the start date.

What happens if adding a month lands on a day that doesn't exist?

The tool clamps the result to the last day of that month. For example, adding a month to January 31 gives February 28 (or February 29 in a leap year), not a date in March.

Does it matter which date I put first in "Months between dates" mode?

No. If the end date is earlier than the start date, the tool sorts the two dates before calculating, so the result is the same either way.

Is my data sent to a server?

No. The calculation runs in your browser as you type. If you're signed in, your dates sync privately to your account; if you're signed out, nothing is saved anywhere.