Months to Days Calculator
Months have 28 to 31 days, so “how many days is six months?” has more than one correct answer. Enter a number of months and a start date to get the exact count of calendar days, with month lengths and leap years taken into account. The calculator also shows the average-based answer and the 30-day banking convention for comparison.
- Runs in your browser
- No sign-up
- Free to use
Whole months give an exact answer from a start date; decimals use averages.
How to use Months to Days Calculator
- Enter the number of months.
- Choose the start date, or press Today.
- Read the exact number of days and the end date.
- Compare with the average and 30-day results.
Months to Days Calculator features
Exact count
Real calendar days from your start date, including leap years.
End date
Shows the date the months end on.
Average method
30.436875 days per month, the Gregorian average.
30-day convention
Used in some financial calculations.
Fractional months
Decimals are taken of the following month.
Month-end handling
Explains when 31 January + 1 month lands on 28 February.
When to use Months to Days Calculator
- Converting a contract or subscription term into days.
- Counting days in a probation or notice period.
- Converting age or gestation in months.
- Estimating a project duration.
Months to Days Calculator FAQ
How many days are in a month on average?
30.436875: the 365.2425 days of the average Gregorian year divided by 12.
How many days are in 6 months?
It depends on the months: between 181 and 184 days. From 1 January in a common year it is 181; from 1 July it is 184.
Why do the exact and average results differ?
The exact count uses the actual months after your start date; the average assumes every month has the same length.
What is the 30-day convention?
Some banking and accounting calculations treat every month as 30 days and the year as 360 days to simplify interest.
What happens on 31 January plus one month?
There is no 31 February, so the period ends on the last day of February, as most legal and financial conventions assume.
How are decimal months handled?
Whole months are counted on the calendar, and the fraction is taken of the next month’s length.
Why months are awkward
Days and weeks have fixed lengths; months do not. The Gregorian calendar has months of 28, 29, 30 and 31 days, a legacy of Roman reforms rather than any natural cycle. Converting months to days therefore depends on which months are meant.
When a start date is known, the exact answer is easy for a computer: move forward the given number of calendar months and count the days. That is what the calculator does, handling leap years and the case where the start day does not exist in the target month.
Without a start date, an average is the best estimate. The Gregorian year averages 365.2425 days over its 400-year cycle, which gives 30.436875 days per month. Finance sometimes uses a simpler convention of 30 days per month. Each answer is correct for its purpose.
For anything contractual, such as a notice period, a warranty or a loan term, the governing document decides how months are counted. Most use calendar months from a specific date, which is the exact result shown here; check the wording when the difference of a few days matters.