Workforce planning / contractor calculators

Project Duration Calculator

Estimate working days and workweeks for a defined scope using crew size, productivity, efficiency, and delay allowances.

01 / Inputs

Use your crew numbers

Example values are loaded. Replace them with your own figures. Every field is required; enter 0 where it applies and is allowed.

Remaining work quantity (units)Use the same quantity unit as the productivity rate. Minimum 0.

Baseline productivity per worker-hour (units/hour)Use a rate at full efficiency. Do not reduce an already observed rate twice. Greater than 0.

Crew size (workers)Greater than 0, whole number.

Paid hours per worker per day (hours/day)Greater than 0, maximum 24.

Expected production efficiency (%)100% uses the baseline rate unchanged; lower values allow for lost production time. Greater than 0, maximum 100.

Additional delay allowance (workdays)Added to production days, without duplicating downtime already in efficiency. Minimum 0, whole number.

Working days per week (days/week)Greater than 0, maximum 7, whole number.

02 / Result

Your working numbers

Scheduled working days

workdays

Expected units per crew-day (units/crew-day): 408.00
Production workdays (rounded up) (workdays): 9.00
Additional delay workdays applied (workdays): 2.00
Estimated workweeks (workweeks): 2.20
Production labor-hours (unrounded) (hours): 282.35

How the math works

Daily output = workers × paid hours/day × baseline productivity × efficiency ÷ 100. Production workdays = round up(quantity ÷ daily output). Scheduled workdays = production workdays + delay workdays. Workweeks = scheduled workdays ÷ working days/week.

Workforce assumptions

Estimates one scope with a uniform crew and rate, not a multi-trade critical path or a calendar finish date. Weather, holidays, curing, inspections, and dependencies require separate scheduling. With no remaining quantity, duration and delay allowance applied are both zero.

Planning estimate only, calculated locally in your browser. Results are averages from your inputs, not an exact schedule or guaranteed finish date. Confirm crew availability, sequencing, and payroll rules before committing to a customer or bid.

Contractor field notes

Estimate working time for a defined construction scope

The project duration calculator converts remaining quantity and a per-worker production rate into crew output per day. It adjusts for efficiency, rounds production up to whole working days, and adds a separate delay allowance. It estimates one uniform activity, not an entire multi-trade critical-path schedule.

Production capacity determines working duration

Daily output = crew size × hours per worker per day × baseline units per labor-hour × efficiency ÷ 100. Production days = round up(quantity ÷ daily output). Scheduled workdays = production days + additional delay workdays. Estimated workweeks = scheduled workdays ÷ working days per week.

Worked example

For 3,600 square feet, four workers, eight hours per day, a baseline rate of 15 square feet per labor-hour, and 85% efficiency, daily output is 4 × 8 × 15 × 0.85 = 408 square feet. Production takes 3,600 ÷ 408 = 8.82 days, rounded up to nine working days. Add two delay workdays for 11 scheduled workdays, or 2.2 five-day workweeks.

Common estimating pitfalls

Enter a baseline rate and efficiency consistently; avoid counting the same downtime twice.
Delays are additional workdays, not calendar days or an automatic holiday allowance.
More workers do not always increase output linearly; access, equipment, sequencing, and supervision can limit capacity.

Frequently asked questions

Is the result a calendar completion date?

No. It reports working days and equivalent workweeks. Start-day placement, weekends, holidays, weather, and trade dependencies require separate calendar scheduling.

Why round production days up?

A partial final production day still requires a scheduled working day. Workweeks can remain fractional after the whole-day estimate is divided by working days per week.

Should efficiency include the delay allowance?

Use efficiency for expected lost production within working days and the delay allowance for separate interruptions. Do not count the same loss in both. Zero remaining quantity produces zero duration.