How long is that project, in working time?
Estimates are wrong in a predictable direction. Here is what a number of hours actually corresponds to.
Almost exactly a working week
40 h is longer than 2 of the 7 references on this page.
Reference figures are measurements and are rounded; the unit conversion behind them is exact.
| Reference | Size | Yours ÷ theirs | Note |
|---|---|---|---|
| a focused morning | 4 h | 10× | Four hours |
| a working day | 8 h | 5× | |
| a working week | 40 h | 1× | |
| a two-week sprint | 80 h | 0.5× | |
| a working month | 173 h | 0.231× | |
| a quarter | 520 h | 1/13 | |
| a working year | 2,080 h | 1/52 |
Worth knowing
- The planning fallacy is remarkably consistent: people underestimate their own task durations by 20–50% even when they know they have done so before.
- A "week of work" is rarely 40 hours of the task itself. Studies of knowledge work put focused time at three to four hours a day.
Frequently asked
Why are estimates always too short?
Because people estimate the task, not the interruptions, rework and coordination around it. Using how long similar past tasks actually took beats reasoning from the plan.
How many productive hours are in a working day?
Three to four for focused work, in most measurements. The remainder goes to communication, context switching and overhead that is real work but not the task.