This converter changes months into weeks and back again. Because a calendar month has no fixed number of weeks, it uses the long-term average month so results are consistent and reproducible.
How it works
The tool uses the average Gregorian month: a year of 365.2425 days divided by 12 gives 30.436875 days per month, and dividing by 7 gives the weekly figure:
- weeks = months × 4.348125
- months = weeks ÷ 4.348125
Press Swap to reverse the direction. Since real months range from 28 to 31 days, treat the result as an accurate average rather than an exact count for a specific calendar month.
Reference table
| Months | Weeks (approx.) | Common use |
|---|---|---|
| 1 | 4.35 | One-month notice period |
| 2 | 8.70 | Standard trial period |
| 3 | 13.04 | One quarter (Q1, Q2, etc.) |
| 6 | 26.09 | Half-year project phase |
| 9 | 39.13 | Pregnancy (approximate) |
| 12 | 52.18 | Full year in weeks |
Why the result is not a round number
Calendar months have 28, 29, 30, or 31 days — never exactly four or five weeks. The average of 4.348125 weeks per month is mathematically precise for the long-run Gregorian average, but any specific six-month period will be slightly different depending on which months it covers and whether a leap year is involved.
For many planning purposes (sprint estimates, project phases, pregnancy tracking), the result is rounded to the nearest whole week in practice. The table above shows the precise average value; rounding is a judgement call for your specific context.
Practical scenarios where this conversion matters
Project planning — quarterly milestones are commonly described as “13-week sprints” (3 months × 4.348 ≈ 13 weeks). This converter confirms that 3 months and 13 weeks are close but not identical, which matters if you are scheduling by calendar month on one side of a contract and by week number on the other.
Pregnancy tracking — prenatal care often uses weeks of gestation, while everyday conversation uses months. Nine months averages 39.1 weeks, which is why clinical pregnancy length is described as 40 weeks — slightly longer than the calendar estimate.
Loan and lease terms — some financial products specify term in months (e.g. a 24-month car lease) while budget spreadsheets track in weeks. Converting between them helps check how many weekly payments fall within a monthly billing cycle.
Contract notice periods — a 3-month notice period is often quoted as “approximately 13 weeks” on job platforms. The precise figure is 13.04 weeks, which typically rounds to 13.
Everything is calculated locally in your browser — nothing is sent over the network.