Project Hours Calculator

Twenty percent is optimistic

Software estimates in particular suffer from the planning fallacy: studies consistently find real effort exceeding first estimates by 30–100%. A contingency below 20% assumes nothing will be discovered mid-project, which is rarely how projects work. Estimating task by task rather than as a whole reduces the error, which is why this calculator asks for both.

What this page needs from you

This page asks for number of tasks, average hours per task in h, contingency as a percentage and team size. From those it returns total project hours in h, together with per person, working days per person (7.5 h), contingency hours and calendar weeks at 30 h/week. Every figure updates as you type, and nothing you enter leaves your browser.

Hours are decimals, not clock time

One hour and thirty minutes is 1.5 payroll hours, not 1.30. Entering the clock reading understates the shift by twelve minutes, and a 45-minute unpaid break is 0.75 rather than 0.45. This single confusion is the most common error in manual timesheets.

Overtime is counted by the week

Under the US Fair Labor Standards Act, overtime is owed on hours above 40 in a fixed seven-day workweek, and hours cannot be averaged across two weeks of a fortnightly pay period. Several states add a daily threshold on top: California pays overtime above eight hours in a day and double time above twelve, and Alaska, Nevada and Colorado apply daily rules in some industries.