Man-Hour Calculator

A man-hour is one hour of work by one person. It is the basic unit for estimating labour in construction, maintenance and engineering: it converts quantities of work into effort, effort into crew size and duration, and effort into labour cost. This calculator handles both directions, from crew and time to man-hours, and from quantities and norms to man-hours.

How to use it

1. Enter the crew size, working hours per day and number of days to get the total man-hours.
2. Or enter the quantity of work and a productivity norm, such as man-hours per m³, to get the required man-hours.
3. Add the hourly labour rate to estimate labour cost.

Formulas

• Man-hours = Workers × Hours per day × Days
• Required man-hours = Quantity × Norm (man-hours per unit)
• Duration (days) = Required man-hours / (Workers × Hours per day)
• Labour cost = Man-hours × Hourly rate

Worked example

A crew of 6 works 8 hours a day for 5 days: 6 × 8 × 5 = 240 man-hours. If shuttering for a slab requires 1.6 man-hours per m² and the slab is 300 m², the task needs 480 man-hours. With the same crew it takes 480 / 48 = 10 working days. At a rate of 150 per hour, labour costs 72,000.

Planning tips

• Use your own historical norms where possible; published norms vary by region, method and climate.
• Allow for non-productive time: mobilisation, safety briefings, weather and waiting typically reduce effective hours by 10 to 20%.
• Adding workers has limits: beyond the optimal crew size, people get in each other's way and output per person drops.
• Track actual man-hours against planned to calculate productivity factors for future estimates.