Months differ in length, so “months between” is usually counted by calendar date: 15 January to 15 April is three months. Decimal months use the average month length of 30.44 days.
How to use the Month Counter – Months Between Dates
- Start date
- End date
- Include end date
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the start and end dates.
Tips
- Check whether the end date should be included – event durations usually include it, elapsed time does not.
- Months have 28–31 days, so “one month” is counted by calendar date, not as 30 days.
- Use 24-hour time or set AM/PM carefully when entering clock times.
- Time zones and daylight-saving changes are not applied unless the calculator says so.
Common mistakes to avoid
- Counting a 30-day month when a calendar month is meant (or the reverse).
- Forgetting leap years when counting days across February.
- Mixing decimal hours (7.5 h) with clock time (7:30).
Inputs explained
| Field | What to enter |
|---|---|
| Start date | A date |
| End date | A date |
| Include end date | Choose one: No, Yes (+1 day) |
What each result means
- Whole months = monthsbetween([Start date], [End date] + [Include end date])
- and days = [End date] + [Include end date] – addmonths([Start date], [Whole months])
- Decimal months = ([End date] + [Include end date] – [Start date])÷30.436875
- Years = sign([Whole months])×floor(abs([Whole months])÷12)
- and months = sign([Whole months])×mod(abs([Whole months]), 12)
- Total days = [End date] + [Include end date] – [Start date]
Formula
Whole months = calendar months from start to end (the day of month must be reached)Remaining days = end − (start + whole months)Decimal months = days ÷ 30.44Worked example
Inputs — Start date: 2026-10-25; End date: 2027-07-02; Include end date: No.
Results — Whole months = 8; and days = 7; Decimal months = 8.21; Years = 0; and months = 8; Total days = 250.
Frequently asked questions
How many months between two dates?
Count whole calendar months, then the leftover days.
How many days is an average month?
30.44 days (365.25 ÷ 12).
How do I count months for a lease?
Usually by calendar date – a lease from 1 March to 28 February is 12 months.
What formula does the Month Counter – Months Between Dates use?
Whole months = calendar months from start to end (the day of month must be reached).