Counting whole weeks between two dates is just simple date subtraction divided by seven — the trick is choosing between whole weeks and a fractional answer.
Dates in Excel are stored as day numbers, so subtracting them gives days; dividing by 7 gives weeks.
The example
A project starts Jan 1 and ends Mar 12, 2026, and you want the span in weeks.
| A | B | |
|---|---|---|
| 1 | Label | Value |
| 2 | Start date | 2026-01-01 |
| 3 | End date | 2026-03-12 |
| 4 | Days apart | 70 |
| 5 | Whole weeks | 10 |
The formula
Take the day gap and divide by seven, keeping only the whole part:
How it works
Step by step:
B3-B2subtracts the two date serials and returns the number of days between them (70).- Dividing by 7 converts days to weeks (10.0 here).
INTdrops any fraction so you get whole weeks only.- Use
MOD(B3-B2,7)alongside it to get the leftover days.
For an exact fractional answer (10.0, 10.4, …) just use =(B3-B2)/7 without INT.
Try it: interactive demo
Enter the two dates as day counts apart — the week math updates live.
Variations
Whole weeks and leftover days
Pair INT with MOD to report both numbers.
Round to the nearest week
Use ROUND instead of INT when you want the closest week, not the floor.
Pitfalls & errors
If the result shows as a date, set the cell format to General or Number.
Make sure both cells are real dates, not text. A left-aligned date is usually text — fix it with DATEVALUE.
Practice workbook
Frequently asked questions
Does this count partial weeks?
Why divide by 7 and not use a week function?
Can I get weeks between in business days?
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