Project Hours to Calendar Weeks Calculator
Convert a project’s estimated hours into calendar weeks and a finish date, given how many hours go into it each week.
How it works
calendar weeks = total hours ÷ hours per week · finish date = start + ⌈weeks⌉ × 7 − 1 day
Effort and elapsed time are different things: 160 hours of work does not mean 160 hours on the calendar. Dividing the total effort by how many hours you actually devote each week converts effort into calendar weeks, and multiplying the rounded-up weeks by seven projects a finish date. The fewer hours per week you can commit, the longer the wall-clock schedule stretches — which is why a part-time project spanning many weeks can still be a modest number of effort-days.
Worked example
A 160-hour project at 20 hours a week is 160 ÷ 20 = 8 weeks. Starting September 16, 2026, it finishes about November 10, 2026 — equivalent to 20 eight-hour days of effort.
Frequently asked questions
Why round the weeks up for the date?
A partial final week still occupies a whole week on the calendar, so the finish date uses the rounded-up number of weeks. The unrounded figure is shown separately as the true effort-to-time ratio.
What are the "8-hour days"?
It re-expresses the total effort as full working days for a quick sanity check — useful when comparing a part-time schedule against what the same work would take full time.
Does it account for holidays or time off?
No — it assumes a steady weekly effort. If you will pause the project, either lower the hours-per-week to reflect the average or add the break to the finish date.
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This calculator is for educational purposes. Double-check important results before acting on them.