Work Duration and Labour Hours Calculator

How many days will a job take?

Duration is found in two steps. First the total effort: labour hours = quantity × labour hours per unit. Then that effort is divided by what the crew can deliver in a day: duration = labour hours / (workers × hours per day). The result is in working days.

How many workers are needed?

If the duration is fixed, the calculation is turned around: workers = labour hours / (target duration × hours per day). The number of workers is rounded up. The tool also shows how long the job really takes with the rounded crew.

Where does the hours per unit figure come from?

The most reliable source is what your own crew has achieved on similar work. Failing that, you can start from the labour times in unit rate analyses. Add skilled and helper hours together and enter one figure. You can add a separate lost time allowance for weather, waiting and material delays.

Example

Take 500 m² of plastering at 0.8 labour hours per square metre. The total effort is 400 labour hours, or 50 labour days. A crew of six working 8 hours a day finishes in 400 / 48 = 8.33 working days, so 9 days. Finishing the same job in 5 days needs 10 workers.

Limits

The calculation assumes that doubling the crew halves the duration. In confined areas that does not hold. The result is in working days, so add holidays and weather when converting to calendar time. The overall duration of linked activities needs a critical path calculation.