Months Between Dates Calculator
Need the number of calendar months between two dates? Enter a start and end date and this calculator counts whole months the way a calendar actually works, not by dividing days by an average month length.
Example
This breakdown is always calculated from the actual calendar span between the two dates. Unlike a plain day count, a months-and-days figure has no single well-defined "count both endpoints" adjustment, so there is no inclusive option here; if you need that distinction, the day count on the Date Difference Calculator has it.
From January 15, 2024 to April 20, 2025 is 15 months and 5 days.
Calendar months, not an average
The month count walks the real calendar, not the total day count divided by an average month length (30.44 days). That distinction matters at the edges: a manual calculation that assumes every month is 30 days will disagree with the real calendar whenever the span crosses a February or a run of 31-day months. This calculator counts whole calendar months, then reports the leftover days separately, so the two figures always agree with each other.
Common uses
- Subscriptions and billing. Confirming how many monthly cycles have run between two dates.
- Tenancy and lease length. Working out the exact term of a lease that does not start or end on a clean month boundary.
- Warranty and guarantee periods. Checking how many months have elapsed against a stated coverage window.
- Loan and probation periods. Confirming a required number of months has genuinely passed.
Frequently asked questions
Months between dates: practical examples and tips
Use this months between dates calculator to track subscription renewals, measure tenancy length, or verify warranty coverage. Enter any start and end date, and the months between dates calculator returns the exact calendar-month count plus leftover days. For payroll and HR, run the months between dates calculator to confirm probation periods and notice windows. Because this months between dates calculator walks the real calendar, it handles February and leap years correctly — no manual adjustment needed.
Calendar months vary from 28 to 31 days, which is why a simple day-count divided by 30 gives misleading answers. The Wikipedia article on the month explains how the Gregorian calendar defines each month's length. When you need the months between dates for contracts or billing, always use the calendar-month count rather than an average. This free months between dates calculator is perfect for leases, loans, and
People search for months between dates for reasons that range from ordinary to life changing. A new parent wants to know exactly how many months old their baby is. Someone compares two loan tenures. A project manager blocks out milestones. The question looks simple until you try to answer it, because months are the one unit of time that refuses to sit still. A month can be 28, 29, 30, or 31 days long, and that single fact is responsible for most of the confusion.
Type two dates into the months between dates calculator at the top of this page and you get your answer in seconds, along with a breakdown in weeks and days so nothing stays hidden. The rest of this guide explains what the calculator does behind the scenes, how to do the same math by hand, and how to run it in Excel or Google Sheets. If you only needed the number, you already have it. If you want to understand where it comes from, read on.
How the months between dates calculator works
The tool asks for exactly two inputs and handles everything else. Here is the sequence:
- Enter the start date. Any calendar date works, past or future. Use the earlier of your two dates for the standard result.
- Enter the end date. This is the later date. The calculator accepts dates in either order, but the result reads most naturally when the end date comes second.
- Read the result. You see the number of full months first, then a breakdown showing weeks and days, so partial months are visible instead of being rounded away silently.
The default method counts complete calendar months. A complete month runs from a date to the same date in the next month, so January 15 to February 15 is one full month, while January 15 to February 14 is not. Any leftover days appear separately in the breakdown. This matches how bills, leases, and loan terms treat months in practice.
Full months vs decimal months: two ways to count
Two different answers can both be right, because months get counted two different ways. The difference matters whenever you compare results from different tools, so it is worth ten minutes of your attention.
Take the same pair of dates: January 15 to October 14, 2026. First, count full months. Walk forward by month anniversaries: February 15 is one, March 15 is two, and so on until September 15, which is eight. October 15 has not arrived yet, because the end date stops at October 14, so the eighth anniversary is the last complete one. The result is 8 full months, with 29 days left over (September 15 to October 14).
Now count decimal months. Add up every day between the dates: 16 days left in January, plus 28 in February, 31 in March, 30 in April, 31 in May, 30 in June, 31 in July, 31 in August, 30 in September, and 14 in October. That is 272 days. Divide by the average month length of 30.4375 days (365.25 divided by 12) and you get 8.94 months.
| Method | Jan 15 to Oct 14, 2026 | Main strength |
|---|---|---|
| Full months | 8 months, 29 days | Matches how billing, leases, and loan terms work |
| Decimal months | 8.94 months | Works in formulas, averages, and rate math |
Use full months when the answer needs to match a real calendar cycle. Billing periods, subscription renewals, rental agreements, and a baby's age in months all run on this method. Nobody says a baby is 8.94 months old at a checkup. Use decimal months when the number feeds a formula: interest accrual, project velocity, statistical averages, and prorated charges. The decimal form behaves like any other number, which is exactly what formulas need.
The main takeaway is simple. When two calculators disagree, check which method each one uses before deciding one of them is wrong.
How to calculate months between two dates by hand
The hand method takes under a minute once you see the pattern. Work through this example: March 10, 2024 to October 14, 2026.
- Count the whole years first. March 2024 to March 2026 is two full years. Multiply by 12 to get 24 months.
- Count the leftover months. March to October is 7 months. April is one, May two, June three, July four, August five, September six, October seven.
- Add the two parts. 24 plus 7 gives 31 months.
- Adjust for the day of the month. The start day is the 10th and the end day is the 14th. Because the end day is equal to or later than the start day, no adjustment is needed. The answer is 31 full months.
The day-of-month adjustment in step 4 is the part most people miss. If the end date had been October 5 instead of October 14, the fifth of the month would not have completed the 31st month yet, and the answer would drop to 30 full months with 25 remaining days. The rule: when the end day is earlier than the start day, subtract one month and count the leftover days from the last completed anniversary.
A second check helps with long spans. Multiply nothing and trust nothing; instead, verify with a midpoint. March 10, 2024 plus 31 months lands on October 10, 2026. The end date of October 14 sits four days past that anniversary, which confirms 31 complete months with days to spare. That quick landing check catches most arithmetic slips.
Months between dates in Excel and Google Sheets
Spreadsheets have a purpose-built function for this, though it hides in the documentation. DATEDIF calculates the difference between two dates in a unit you choose, and the "M" unit returns full months. Put your start date in A2 and your end date in B2:
=DATEDIF(A2,B2,"M")
This returns the number of complete months. It ignores partial months entirely, which matches the full-month method described above. Both Excel and Google Sheets support this formula with the same syntax.
For months remaining after full years, use the "YM" unit:
=DATEDIF(A2,B2,"YM")
This is handy for age-style results. If A2 holds a birth date and B2 holds today, combine =DATEDIF(A2,B2,"Y") for years with =DATEDIF(A2,B2,"YM") for the extra months, and you get a clean "X years, Y months" answer.
For decimal months, YEARFRAC does the work. It returns the fraction of a year between two dates, so multiplying by 12 converts it to months:
=YEARFRAC(A2,B2)*12
YEARFRAC takes an optional basis argument that controls the day-count convention. The default uses a 30-day month convention, which is standard in finance. For a calendar-accurate result, use basis 3, which counts actual days over a 365-day year:
=YEARFRAC(A2,B2,3)*12
One warning about DATEDIF: it returns an error if the start date is later than the end date, and it silently drops partial months. If you need the leftover days too, add =DATEDIF(A2,B2,"MD") alongside the month count.
Why month math gets tricky
Days and years are stable. Months are not, and three quirks cause nearly all the arguments.
Month-end dates
The trouble starts when a date has no counterpart in the next month. January 31 to February 28 looks like one month, but February 28 is not the 31st, so no anniversary was reached. Different tools resolve this differently, and the table below shows the common readings:
| Start date | End date | Common reading |
|---|---|---|
| January 31 | February 28 | 0 full months, 28 days (no anniversary reached) |
| January 31 | March 31 | 2 full months |
| January 30 | February 28 | 0 full months, 29 days |
| February 28 | March 28 | 1 full month |
The calculator on this page follows the anniversary rule: a month counts only when the same calendar date arrives. That keeps results consistent even when the months involved have different lengths.
February and leap years
February is the shortest month and the only one that changes length. In leap years it has 29 days instead of 28, which adds one day to any span that includes February 29. Full-month counts rarely change because of it, but day totals and decimal months shift by a fraction.
The leap-year edge case worth knowing involves February 29 birthdays. From February 29, 2024 to February 28, 2025 is 12 full months by the anniversary rule used here, even though no February 29 exists in 2025. Most legal and administrative systems treat February 28 as the anniversary in non-leap years. If your situation has its own convention, check it rather than assuming.
Months of different lengths
A span of "one month" can contain anywhere from 28 to 31 days. April 15 to May 15 is 30 days. May 15 to June 15 is 31 days. Both are exactly one full month. This is why converting days to months with a fixed divisor like 30 is only an approximation, and why the full-month method exists as the calendar-honest alternative.
Common uses
Month counting shows up in more places than most people expect.
Pregnancy tracking is the most searched use. A full-term pregnancy runs about 9 months, and expectant parents convert constantly between weeks and months. Forty weeks divides into roughly 9.2 calendar months, which is why week counts and month counts never line up neatly. Pediatricians continue the pattern after birth, tracking infants by months (sometimes weeks) until age two, because development moves too fast for yearly buckets.
Loan and lease terms are written in months. A 36-month car loan, a 12-month lease, a 60-month mortgage schedule. Comparing two loans means comparing their month counts directly, and an off-by-one error changes the total interest. Project timelines work the same way: quarters are 3-month blocks, roadmaps are measured in months, and milestone dates are month anniversaries of the kickoff.
Subscription and billing cycles round out the list. Monthly billing charges on the same calendar date each month, and prorated refunds for mid-cycle cancellations need the decimal-month math from the section above. Service contracts, warranties, and insurance policies all define their terms in months, so knowing how to count them precisely saves real money.
Frequently asked questions
How many months are between January and October 2026?
9 months. Counting from the start of January to the start of October spans nine calendar months: February, March, April, May, June, July, August, September, and October. If you mean January 1 to October 31, that is 9 full months plus 30 days.
How do I calculate months between two dates in Excel?
Use =DATEDIF(start_date, end_date, "M"). Put the start date in one cell and the end date in another, for example =DATEDIF(A2,B2,"M"), and Excel returns the number of complete months. Add =DATEDIF(A2,B2,"YM") if you also want the months remaining after full years. The same formulas work in Google Sheets.
What is the difference between full months and decimal months?
Full months count complete calendar months between two dates, so January 15 to October 14, 2026 is 8 full months with 29 days left over. Decimal months divide the total day count by 30.4375 (the average month length), giving 8.94 for the same span. Full months match billing cycles and legal terms; decimal months feed formulas and statistics.
How many months is 90 days?
About 2.96 months. Divide 90 by 30.4375, the average length of a calendar month. In practice, 90 days spans just under 3 full calendar months, so most billing contexts would treat it as 2 full months with about 30 days remaining.
How many months between March 2024 and October 2026?
31 months. Count two full years from March 2024 to March 2026 (24 months), then add the 7 months from March to October. The exact day of the month can adjust this by one, as explained in the hand-calculation section above.
Does the calculation include both the start and end month?
The full-month method counts complete months between the dates, not both endpoint months as whole months. January 15 to March 15 is 2 full months: the spans January 15 to February 15 and February 15 to March 15. The endpoint dates themselves are boundaries, not extra months. Any leftover days after the last complete month appear separately in the breakdown.
How do leap years affect month calculations?
A leap year adds February 29, which adds one day to the total day count of any span that includes it. Full-month counts almost never change because of a leap day, but decimal-month results shift slightly and day totals grow by one. The February 29 birthday edge case is the main exception: most systems treat February 28 as the anniversary in non-leap years.
What is 9 months from today?
July 14, 2027. Counting forward from October 14, 2026: November 14 is one month, December 14 two, January 14 three, February 14 four, March 14 five, April 14 six, May 14 seven, June 14 eight, and July 14 nine. This is the figure most people want when tracking a pregnancy from conception or planning a 9-month project.
What is 3 months from today?
January 14, 2027. From October 14, 2026, count forward: November 14 is one month, December 14 is two, and January 14 is three. Quarterly planning, 90-day goals, and season-length projects commonly use this span.
Can I count partial months?
Yes. You have two honest options. Report full months plus the leftover days, for example 8 months and 29 days, which matches how billing and contracts treat partial periods. Or use decimal months, for example 8.94, which plugs directly into formulas. Pick the format your reader expects and say which one you used.
Related calculators
Age calculator: your exact age in years, months, and days from any birth date.project planning. Bookmark the months between dates calculator for quick, accurate month differences throughout the year.
Months ago calculator: count backward from today to find what date fell a given number of months ago.
Years between dates calculator: measure longer spans in years, months, and days.
Date difference calculator: the full breakdown of days, weeks, months, and years between any two dates.