Days Between Dates Calculator
Count calendar days or business days
How the Calculator Works
Here is how this days between days calculator works:
Calendar Days
The total number of days between two dates counts every day — weekdays, weekends, holidays. It’s the raw calendar distance between the two dates.
Example: From January 15 to March 31 is 75 calendar days.
Use this for:
- Legal and contractual deadlines (most use calendar days)
- Age calculations
- Countdowns to events
- Loan and lease durations
Business Days
Business days exclude Saturdays and Sundays. The calculator loops through every date in the range and counts only Monday through Friday.
Example: From January 15 to March 31, there are approximately 54 business days (depending on the year).
Use this for:
- Project scheduling and sprints
- Invoice payment terms (Net 30 business days is common)
- HR and hiring timelines
- Anything where your team only works weekdays
Note: the calculator does not account for public holidays, since holidays vary by country, region, and company. For holiday-aware business day counts, use Excel’s NETWORKDAYS function.
How to Use This Calculator
- Start Date — enter or pick your starting date. Defaults to today.
- End Date — enter your target date. Defaults to 30 days from now.
- Swap button (⇄) — click to flip the two dates. Useful when you already know the end and want to count backward.
- Exclude weekends — check this to show business days in the main breakdown. The business day count is always calculated either way; checking the box just emphasizes it.
- Calculate — click to see your results.
If your end date is before your start date, the calculator still works — it shows the absolute number of days and notes that the end date comes first.
How to Count Days Between Dates in Excel
Excel has several functions for this, and the right one depends on what you need.
DAYS function (simplest)
=DAYS(end_date, start_date)Returns the number of days between two dates. Note the argument order: end first, then start. This is the opposite of what you might expect.
=DAYS("3/31/2025", "1/15/2025")Returns 75.
DATEDIF function (flexible but undocumented)
=DATEDIF(start_date, end_date, unit)The unit can be:
- “D” for total days
- “M” for complete months
- “Y” for complete years
- “MD” for days ignoring months and years
- “YM” for months ignoring years
Important gotcha: DATEDIF is an undocumented function in Excel. It was inherited from Lotus 1-2-3 and Microsoft has never officially documented it in modern Excel. It won’t appear in the autocomplete dropdown when you type it. But it still works in all modern versions of Excel, including Excel 365. Just type it exactly as shown.
=DATEDIF(A1, B1, "Y") & " years, " & DATEDIF(A1, B1, "YM") & " months, " & DATEDIF(A1, B1, "MD") & " days"This produces a human-readable breakdown like “3 years, 2 months, 14 days.”
NETWORKDAYS (business days, excluding weekends)
=NETWORKDAYS(start_date, end_date)Counts weekdays only (Monday-Friday). You can add an optional third argument for a list of holidays to exclude.
=NETWORKDAYS(A1, B1, holidays_range)NETWORKDAYS.INTL (custom weekends)
=NETWORKDAYS.INTL(start_date, end_date, weekend, holidays)Use this if your work week isn’t Mon-Fri. The weekend argument lets you specify which days are non-working. For example, 2 = Saturday and Sunday, 7 = Friday and Saturday (common in Middle Eastern countries).
Common Use Cases
Project deadlines. Count from today to the project due date. Check the business days count to see how many actual working days you have. If it’s less than you thought, that’s a useful reality check.
Contract and lease duration. Most contracts count in calendar days. “30 days notice” usually means 30 calendar days from the date of notice. Use this calculator to find the exact expiry date.
Invoice payment terms. “Net 30” typically means 30 calendar days, but “Net 30 business days” means something different — and significantly longer. Know which one your agreement says.
Employee tenure and anniversaries. Calculate how long someone has worked at the company, or how many days until their work anniversary.
Age calculations. Calculate how many days old you are, or how many days until a birthday.
Loan maturity. Many loan terms are expressed in days. A 90-day loan from January 15 matures on April 15 (or April 14 — check how your lender counts the start date).
Common Mistakes to Avoid
Not checking whether your agreement uses calendar days or business days. “30 days” in a contract almost always means calendar days. Assuming it means business days can cause you to miss a deadline by more than a week.
Using DAYS instead of DATEDIF for month/year breakdowns. DAYS gives you total days. To express a duration as “2 years, 3 months, 14 days,” you need DATEDIF with the YM and MD units.
Off-by-one errors in Excel. Whether you include or exclude the start and end dates changes the count by 1 or 2. DAYS(B1, A1) counts the gap between the two days, not inclusive of both. If you want to include both the start and end day, add 1 to the result.
Forgetting that NETWORKDAYS is inclusive. NETWORKDAYS counts both the start date and end date if they’re weekdays. This means NETWORKDAYS(“Mon”, “Mon”) returns 1, not 0. Adjust for this if your counting convention excludes the start day.
Using date subtraction for month or year differences. A1 – B1 in Excel gives you total days. It does not tell you how many months or years have passed. January 31 to March 1 is 29 or 30 days, but is it 1 month or 2? DATEDIF with “M” gives you the correct whole-month count.
FAQ
How do I calculate business days in Excel?
Use =NETWORKDAYS(start_date, end_date). This returns the count of weekdays (Monday-Friday) between the two dates, inclusive. Add a third argument with a range of holiday dates to exclude those as well.
What is DATEDIF in Excel and why doesn’t it show in autocomplete?
DATEDIF is a date difference function that Excel inherited from Lotus 1-2-3. Microsoft kept it for backward compatibility but never officially documented it in modern Excel, so it doesn’t appear in the function dropdown. It still works fine — just type =DATEDIF( and Excel will run it.
Does the calculator include the start date and end date in the count?
The calculator measures the gap between dates, which means it does not include both endpoints. From January 1 to January 5 is 4 days, not 5. If your use case requires including both the start and end date, add 1 to the result.
What if I need to exclude holidays as well as weekends?
This calculator counts only calendar days and excludes weekends for business days. For holiday exclusions, use Excel’s NETWORKDAYS(start, end, holidays) function with a list of your specific holiday dates.
Can I calculate how many days until a future date?
Yes. Set Start Date to today and End Date to your target date. The result is the number of days remaining.
How accurate are the years and months breakdowns?
The year breakdown uses 365.25 days per year (accounting for leap years). The month breakdown counts whole calendar months. Both are approximations for display purposes. For precise legal or contractual calculations, use the total calendar days figure.
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