📅 Project Duration Calculator
Estimate project duration based on work scope, crew size, and productivity rates.
Quick Formula
Basic Duration
Duration = Total Work ÷ (Crew Size × Hours per Day × Productivity Rate × Working Days per Week)
With Buffer
Duration with Buffer = Base Duration × (1 + Contingency Factor)
Common Duration Factors
Weather Days
| Climate | Weather Days per Month |
|---|---|
| Mild | 1-2 days |
| Moderate | 2-3 days |
| Severe | 3-5 days |
Working Days
Working Days = Calendar Days - Weekends - Holidays - Weather Days
Common Calculations
Example 1: Simple Project
Work: 5,000 sq ft framing Crew: 4 workers Productivity: 75 sq ft/hr per worker Hours: 8 hours/day Working days: 5 days/week
Calculation:
- Daily output: 4 × 8 × 75 = 2,400 sq ft/day
- Days needed: 5,000 ÷ 2,400 = 2.08 days
- With 20% buffer: 2.08 × 1.20 = 2.5 days (3 days)
Example 2: Complex Project
Work: Multiple trades, 10,000 sq ft building Crews: Various (concrete, framing, MEP, finishes) Schedule: Sequential phases
Phases:
- Site work: 2 weeks
- Foundation: 2 weeks
- Framing: 4 weeks
- MEP: 3 weeks
- Finishes: 4 weeks
- Total: 15 weeks
Contingency Factors
| Project Type | Contingency |
|---|---|
| Simple, repetitive | 10-15% |
| Standard | 15-20% |
| Complex | 20-30% |
| High-risk | 30-40% |
Interactive Calculator
Total scope of work in units (e.g., SF, LF, CY)
Expected daily production output
Scheduled work days per week (default 5)
Expected weather delay as percent of work days (default 10%)
Related Resources
- Crew Productivity Calculator - Calculate productivity
- Project Startup Checklist - Project planning
Plan for Delays
Always add contingency to duration estimates. Weather, material delays, and unforeseen conditions are common.