About the Months Between Dates Calculator
Contracts, leases, warranties, pregnancies, loans and subscriptions are often measured in months, and counting them by hand across different month lengths is easy to get wrong. This calculator takes any two dates and tells you the number of whole calendar months between them, plus the leftover days. It also gives the result as years, months and days, as a decimal number of months, and as total days and weeks. If you enter the dates in reverse order, it swaps them for you and says so.
Updated October 2026
How to use the Months Between Dates Calculator
- 1Pick the start date.
- 2Pick the end date. The order doesn't matter.
- 3Read the number of whole months and leftover days.
- 4Check the years, months and days breakdown.
- 5Use the decimal months or total days if your form needs them.
Where month counts are used
- Leases and notice periods that say three months from a start date.
- Warranties of 12 or 24 months from purchase.
- Pregnancy and baby age in months.
- Loan terms, installment plans and subscription periods.
- Project reports that need elapsed months between milestones.
A worked example
From 31 January to 1 March, many people expect 1 month. The calculator counts one whole month, since 31 January plus one month lands on 28 February (or 29 in a leap year), and then 1 or 2 leftover days. The same logic stops the result from jumping around when a start date falls at the end of a long month.
Be careful with legal or financial uses. Some contracts count a month as 30 days, others use calendar months, and a few say that a period ends the day before the same date in the later month. The calculator uses the standard calendar method, which matches most everyday definitions, but always check the wording of your agreement or ask the other party how they count.
Other date tools
Use the Days Between Dates calculator for day counts and business days, the Date Calculator to add or subtract time, the Age Calculator for birthdays, the Working Days Calculator for business days and the Week Number Calculator to find the week of the year. The Pregnancy Due Date Calculator also counts weeks and months.
Features
- Whole months plus leftover days
- Years, months and days breakdown
- Months as a decimal
- Total days and weeks
- Handles reversed dates and leap years
- Short month rules handled
Frequently asked questions
How do you count months between two dates?
Count each full calendar month from the start date. From 15 January to 15 October is exactly 9 months. From 15 January to 3 October is 8 months and 18 days, because the ninth month is not yet complete.
How does it handle months of different lengths?
Adding a month to the 31st of January gives the last day of February, since February has no 31st. The calculator applies this rule when it counts whole months, so results stay sensible around month ends.
What is the decimal number of months for?
Some forms, rent calculations and subscription fees use fractional months. The decimal divides the leftover days by the length of the month in which they fall, so 8 months and 18 days is about 8.6 months.
Does the order of the dates matter?
No. If the end date is earlier than the start date, the calculator swaps them and tells you. The answer is the same size either way.
Are leap years included?
Yes. The days are counted on the actual calendar, so 29 February is counted in leap years. From 29 February 2020 to 28 February 2021 is 11 months and 30 days; the next day completes the year.
Why is the total in days different from months times 30?
Months have 28 to 31 days, so months times 30 is only an approximation. Total days from the real calendar is the safer figure for anything with a legal or financial meaning.