Before you start
Effort-to-Duration Converter
Turn hours of work into a finish date the calendar will actually keep, by counting what simple division leaves out: other work, meetings, time off, late starts and holidays.
Type the team in, or read a team list from a .xlsx or .csv inside your browser. Nothing is uploaded.
Choose a start date.
Working calendar Monday to Friday, US federal holidays, weekend holidays moved to the nearest working day change
Who is doing it
Blank hours take the standard day. Time off: dates or ranges like 2026-10-12 to 2026-10-16, separated by semicolons.
A team list
Drop a spreadsheet here
Optional. Name, allocation, hours a day, time off and a start date, one row per person.
| Name | Allocation | Hours a day | Time off | Joins on | Remove |
|---|---|---|---|---|---|
Why “eighty hours, two people, one week” is usually two
Dividing effort by the team’s paid hours assumes everyone does nothing else. In practice each person is shared with other work, loses part of every day to meetings and email, takes time off, and some join after the start. None of those is a surprise, and together they routinely double the answer. So the tool gives both dates, the division and the calendar, and shows where every paid hour between them went.
Allocation and time left for the work are different losses
Allocation is the share of a person given to this work at all: a developer split between two projects is at 50%. Time left for the work is what remains of that share after meetings, email and admin, and it applies to everyone, including people who are fully allocated. The simplest way to set it is from a real week: a 40-hour week with 8 hours of meetings leaves 80%.
Time off falls on particular days
A week off is not a 2% reduction spread across the project. It is five days on which one person contributes nothing, and if that week sits in the middle of the work, the finish moves by it. So the tool walks the calendar one working day at a time, with each person’s time off and start date, and the public and company holidays from the calendar settings.
More people are not always faster
Some work cannot be split further than a few people: one environment to deploy to, one document to write, one decision to make. If you set the most people who can usefully work on it at once, the extra people’s time is counted as idle, not as progress, and the finish shows it. This is the honest version of a well-known observation about late projects, without pretending to measure how much slower a crowd gets.
What this does not do
It does not estimate the effort; the hours are yours, and the Three-Point Estimate Calculator can put a range on them. It treats everyone as equally productive on the work and assumes handovers cost nothing, and it knows nothing about dependencies between tasks. For a single piece of work, or a workstream that behaves like one, it gives a date that accounts for the people doing it.