Guides/Weeks between two dates

How many weeks between two dates

Weeks are just groups of seven calendar days. Once you know the day count, divide by 7 for whole weeks and keep the remainder.

Formulas

• Whole weeks = floor(days ÷ 7)
• Leftover days = days mod 7
• Exact weeks (if divisible) = days ÷ 7

Decide first whether the end date is inclusive. “From Mon 1 to Mon 15” can be 14 days (exclusive end) or 15 (inclusive) depending on the rule.

Worked examples

1. 21 days apart: 21 ÷ 7 = exactly 3 weeks.
2. 30 days: 30 ÷ 7 = 4 weeks + 2 days.
3. 10 days: 1 week + 3 days.
4. Project span: 1 Jan → 1 Apr in a non-leap year is 90 days → 12 weeks + 6 days (exclusive of end, confirm your calendar).
5. Business weeks: five weekdays ≠ one calendar week of seven days — see business days.

Common mistakes

• Saying “two weeks” when you counted 14 weekdays (that is nearly three calendar weeks).
• Mixing inclusive and exclusive ends when comparing contracts.
• Ignoring leap days on long spans that cross late February.

Get the day count first

Use the freeDate Difference Calculatorfor days between dates, then divide by 7. Related:days between dates·add N days·days until.