How to Calculate Days Between Two Dates (Including Business Days Only)
Learn how to calculate days between two dates, including business days only and weeks, plus use our free days between dates calculator for instant totals.
A deadline, a notice period, a lease term, or a project timeline: plenty of everyday situations boil down to one question, how many days actually sit between two dates. Knowing how to calculate days between two dates manually is straightforward for nearby dates, but it gets genuinely error-prone once a calculation crosses several months or needs to exclude weekends.
This guide covers manual day counting, calculating business days only by excluding weekends, accounting for public holidays, converting a day count into weeks and months, and the most common real-world reasons people need this calculation in the first place.
How to Count Days Between Two Dates Manually
The basic formula
Total Days = End Date − Start Date
The cleanest way to do this by hand is to count the remaining days in the start month, add the full days in every month entirely between the two dates, then add the days elapsed in the end month. For example, from January 15 to March 10: 16 remaining days in January, 28 full days in February, and 10 days into March, for a total of 54 days. Trying to do this by simply counting on a physical calendar works for short spans, but it becomes slow and error-prone once the gap stretches across multiple months.
How to Calculate Business Days Only (Excluding Weekends)
A business day count excludes Saturdays and Sundays, which matters for anything tied to a workweek, such as a shipping estimate, a notice period, or a payment term. A rough shortcut: take the total calendar days, divide by 7 to estimate the number of full weeks, multiply that by 5 to get the weekday count from full weeks, then manually check the remaining partial week for any weekend days that fall inside it.
Using the same January 15 to March 10 example, the 54 total days break down to roughly 39 business days once Saturdays and Sundays are excluded. The exact number depends on which specific day of the week the range starts and ends on, since a 7-day span could contain anywhere from 5 to 7 business days depending on alignment.
Try it yourself
Days Between Dates Calculator
Enter a start date and end date to get total days, business days excluding weekends, weeks and days, and months and days instantly, with a full month-by-month breakdown.
How to Exclude Public Holidays from Your Count
A basic business day count handles weekends automatically, but it does not know about public holidays unless you explicitly account for them. To exclude holidays, identify which specific dates in your range fall on a recognized holiday, then subtract one business day from your count for each one that lands on a weekday (holidays that fall on a weekend do not need a separate subtraction, since they were already excluded).
This step matters most for things like legal notice periods or shipping estimates that are explicitly defined in terms of business days, since miscounting even one holiday can shift a deadline by a full day.
Calculating Weeks and Months Between Dates
Once you have a total day count, converting it into weeks is simple division: divide the total days by 7, and the remainder is the leftover days. The 54-day example above becomes 7 weeks and 5 days.
Converting to months and days is slightly more involved, since months are not a fixed number of days. Subtract the start month from the end month to get a rough month count, then check whether the end date's day number is smaller than the start date's day number. If it is, subtract one month from your count and add the appropriate number of days from the previous month to account for the difference, the same borrowing logic used when calculating age in years, months, and days.
Common Uses for Date Difference Calculations
- Project deadlines, counting down the working days remaining before a delivery date.
- Lease and contract terms, verifying the exact length of an agreement matches what was negotiated.
- Notice periods, confirming an employee or tenant notice satisfies a required minimum number of days.
- Billing and payroll, prorating costs or pay across partial months using a month-by-month breakdown.
- Shipping and delivery estimates, calculating an expected arrival date based on a stated number of business days.
Frequently asked questions
Does counting days between two dates include both the start and end date?
It depends on convention. A simple subtraction of dates gives the number of days elapsed between them, not including the start date itself. If you need an inclusive count that counts both the start and end date, add one day to the result.
What counts as a business day?
A business day is generally any weekday, Monday through Friday. A basic business day count excludes Saturdays and Sundays, but it does not automatically exclude public holidays unless you specifically account for them as well.
How many weeks are between two dates that are 54 days apart?
Divide the total days by 7. 54 days divided by 7 is 7 with a remainder of 5, so the span is 7 weeks and 5 days. The same division approach works for any total day count.
Why would I need a month-by-month breakdown instead of just a total?
A month-by-month breakdown is useful whenever a cost, billing period, or allowance needs to be prorated across partial months, such as splitting rent for a tenant who moves in mid-month or calculating partial-month payroll for a new employee.
Once you understand how to calculate days between two dates manually, including business days and month-by-month breakdowns, the same logic scales to any date range. Use the Days Between Dates Calculator above to get the total, the business day count, and a full monthly breakdown instantly, without doing the borrowing arithmetic yourself.
For related date calculations, see how to calculate age from a date of birth , or for tracking hourly work, see how to calculate work hours with a lunch break.