Inputs
Example data
| Example task | Quantity | Productivity | Crew | Hours/shift | OT/shift | Efficiency | Total labor-hours (approx.) | Duration (workdays approx.) |
|---|---|---|---|---|---|---|---|---|
| Concrete slab placement | 250 m² | 0.30 m² per labor-hour | 6 | 8 | 2 | 95% | ~1,074 | ~18.6 |
| Blockwork laying | 1,200 blocks | 12 blocks per labor-hour | 5 | 8 | 0 | 90% | ~122 | ~3.1 |
Formula used
This calculator estimates total labor-hours and duration using productivity, crew capacity, and adjustment factors.
How to use this calculator
- Enter the work quantity and your unit label.
- Add a realistic productivity rate and select its basis.
- Set crew size, shifts, and working hours per shift.
- Use site efficiency and learning to reflect conditions.
- Add allowances, rework, supervision, and contingency as needed.
- Press “Estimate labor hours” to view results above.
- Use CSV or PDF export for sharing and documentation.
Professional article
Reliable labor forecasting supports bidding, resource planning, and daily control. This calculator links quantity, productivity, crew capacity, and real‑world modifiers so engineers and supervisors can test scenarios consistently and document assumptions for review. Use it early for tenders and later for tracking performance and align daily targets with procurement, availability, and inspections.
Productivity
Start by confirming whether your field rate is per person-hour or per crew-hour. For example, 0.30 m² per labor-hour means one worker produces 0.30 m² each hour. If your rate is 1.8 m² per crew-hour with six workers, select crew-hour to avoid underestimating hours.
Base hours
The core relationship is Quantity ÷ Productivity. A 250 m² scope at 0.30 m² per labor-hour gives 833.33 base labor-hours. If you use crew-hour basis, the calculator converts crew-hours to labor-hours by multiplying by crew size, keeping the estimate comparable across crews and subcontractors.
Adjustment factors
Allowances and rework add expected time for breaks, minor delays, and correction work. Efficiency and learning reflect site constraints and crew familiarity. Apply 5% allowance and 2% rework as multipliers (1.05×1.02). If efficiency is 95%, the calculator divides by 0.95 to increase hours appropriately, making the plan more achievable.
Shift strategy
Duration depends on daily effective labor-hours. Regular hours count fully, while overtime can be discounted with an overtime efficiency (for example 90%) to reflect fatigue and reduced support. Compare options such as adding a second shift, increasing crew size, or adding limited overtime. Pick the option that suits access and safety.
Cost and reporting
When you enter an hourly rate, regular and overtime hours are priced separately using the overtime premium, then optional overhead is added for indirects. Export CSV or PDF to share inputs, results, and assumptions, and update rates as field measurements improve. Keep a log of revisions for audits.
FAQs
1) Should I use “Units per labor-hour” or “Units per crew-hour”?
Use labor-hour when the rate is per person. Use crew-hour when the rate is measured for the whole crew working together. Selecting the correct basis prevents multiplying errors in base hours.
2) What is a reasonable allowance percentage?
Allowances typically cover breaks, small delays, and minor handling. Many teams start with 3–10% and adjust using site history. If you already captured these effects in productivity, reduce the allowance.
3) How do I set site efficiency?
Efficiency reflects access, congestion, weather, logistics, and supervision strength. Use 85–100% for common conditions, lower for restricted sites. Calibrate it by comparing past planned hours versus actual hours.
4) Why does overtime efficiency matter?
Overtime often delivers less output due to fatigue, rework, and reduced support services. Discounting OT hours (for example 90%) keeps the duration estimate realistic while still showing how OT can accelerate completion.
5) Does the calculator include standby or equipment downtime?
Not automatically. Add expected standby through Allowance, Rework, or a reduced Efficiency factor. For equipment-driven tasks, ensure productivity already reflects realistic equipment availability and typical interruption patterns.
6) How is supervision handled?
Supervision factor adds labor-hours for foreman or supervisory time when it is not already embedded in the productivity rate. If your rate came from a crew including supervision, set supervision to 0%.
7) How should I present results in meetings?
Export CSV or PDF and list the key assumptions: quantity, productivity basis, crew size, hours, and adjustment factors. Then provide a best-case and worst-case scenario by varying efficiency and allowance ranges.