Construction Schedule Duration Inputs
Enter production assumptions, site constraints, and phase mix. The calculator converts labor productivity into working and calendar duration.
Example Data Table
These examples show how different field assumptions can change overall schedule length, even when project quantities look similar.
| Package | Quantity | Rate (units/labor-hour) | Crew | Calendar | Key Losses | Approx. Duration |
|---|---|---|---|---|---|---|
| Retaining wall package | 850 m² | 0.92 | 7 | 6 days/week | Weather 6%, access 4%, rework 3% | ~25 calendar days |
| Warehouse slab work | 4,200 m² | 1.75 | 10 | 6 days/week | Weather 8%, overlap 12%, contingency 7% | ~38 calendar days |
| Interior fit-out zone | 2,100 m² | 1.10 | 12 | 5 days/week | Access 9%, rework 5%, holidays 3 days | ~41 calendar days |
Formula Used
Quantity ÷ Productivity rate
Base labor-hours × (1 + Rework %) ÷ Labor efficiency %
Crew size × [Regular shift hours + (Overtime hours × Overtime efficiency %)]
Adjusted labor-hours ÷ Effective crew-hours per day
Base working days ÷ (1 − Weather loss %) ÷ (1 − Access loss %)
Disrupted working days × (1 − Overlap %)
Overlapped working days + (Overlapped working days × Contingency %)
[Total working days × (7 ÷ Working days per week)] + Mobilization + Holidays + Closeout
Finish date is an averaged planning estimate. It does not model named holidays, resource leveling, or contractual milestone logic automatically.
How to Use This Calculator
- Enter the total measured quantity for the work package.
- Use a productivity rate based on labor-hours, not crew-days.
- Set crew size, regular shifts, and any daily overtime.
- Apply labor efficiency to reflect realistic field performance.
- Add weather, access, and rework allowances for site risk.
- Use overlap for concurrent tasks that genuinely compress the schedule.
- Add contingency, mobilization, holidays, and closeout to reflect total project duration.
- Optionally add a start date to forecast an approximate finish date.
FAQs
1) What does this schedule duration calculator estimate?
It estimates the time needed to complete a construction work package by combining quantity, labor productivity, crew size, field losses, overlap, and calendar assumptions into working and calendar durations.
2) Should productivity be entered per labor-hour or per crew-day?
Enter productivity as installed units per labor-hour. That keeps the model consistent when crew size, overtime, and shifts change. If your source data is per crew-day, convert it first.
3) Why are working days and calendar days different?
Working days measure productive field time. Calendar days include the weekly work calendar plus added mobilization, shutdowns, holidays, and closeout periods. Contract schedules usually need both views.
4) How do weather and access losses affect duration?
They act as disruption multipliers. Higher weather or access losses reduce usable production time, which stretches the required working days before contingency and final calendar conversion.
5) What does overlap percentage mean?
Overlap represents schedule compression from parallel activities. For example, exterior work may begin before all structural work is complete. Use conservative values, because too much overlap can hide coordination risk.
6) Why does overtime not shorten the schedule linearly?
Overtime often creates fatigue, congestion, supervision gaps, and reduced productivity. That is why the calculator uses separate overtime efficiency instead of assuming every overtime hour performs like a regular hour.
7) Can I use this for concrete, masonry, finishes, or utility work?
Yes. The model is activity-agnostic. Replace the quantity unit and productivity rate with values appropriate to the scope, then adjust phase percentages and losses to suit the package.
8) Is the finish date ready for contract submission?
It is a planning estimate, not a contractual CPM schedule. Use it for early budgeting, staffing, and scenario testing, then validate it against logic ties, milestones, procurement, and owner constraints.