P6 Activity Duration Calculator
What is a P6 Activity Duration Calculator?
What is P6 Activity Duration?
In Primavera P6, activity duration represents the number of working periods required to complete a discrete scope of work. It links physical Bill of Quantities (BOQ) line items with site crew capabilities.
Formula
Duration (Working Days) = Total Work Quantity ÷ (Daily Production Rate per Crew × Number of Crews × Efficiency Factor)
Variables Explanation
- Total Work Quantity: Net BOQ measurement (e.g., m³, m², metric tons).
- Daily Production Rate: Standard daily output per crew under nominal conditions.
- Number of Crews: Parallel teams assigned.
- Efficiency Factor: Site efficiency modifier (0.50 to 1.00).
How to Calculate
1. Enter total physical work quantity.
2. Input baseline crew daily output rate.
3. Specify active crew count and site efficiency percentage.
4. Review calculated duration in working days and total man-hours.
Worked Example
Project Scope: Concreting 1,200 m³ raft slab.
Crew Production Rate: 40 m³/day per crew.
Assigned Crews: 2 crews.
Job Efficiency: 85% (0.85).
Calculation: Daily Output = 40 × 2 × 0.85 = 68 m³/day.
Calculated Duration = 1,200 ÷ 68 = 17.65 → 18 Working Days.
Practical Construction & Project Controls Use
Used during CPM schedule baseline preparation in Primavera P6, subcontractor productivity verification, and resource loading balancing.
Understanding the Result
A higher duration indicates potential schedule bottlenecks. If duration exceeds the target milestone, planners must add crews or increase daily work shift hours.
Limitations & Assumptions
Assumes continuous material supply and uninhibited site access. Weather disruptions and curing wait times must be modeled using lags or calendars in P6.
Frequently Asked Questions
How does crew size affect activity duration in Primavera P6?
Increasing crew size increases total daily output rate proportionally, reducing the calendar duration required to complete a fixed work quantity.
What is a typical job efficiency factor in construction scheduling?
Civil construction projects typically operate between 75% and 85% efficiency due to site congestion, material handling delays, and safety briefings.
Does P6 automatically round activity duration days?
P6 schedules integer working days based on the assigned calendar. Fractional days are rounded up to the nearest whole working day.
Why is physical quantity preferred over expert judgment for duration?
Quantity-based duration calculation provides an audit trail linked to BOQ drawings, preventing arbitrary schedule compression.
Can this duration be assigned directly to Resource Dependent activities in P6?
Yes, in P6 Resource Dependent activities drive duration directly from assigned resource allocation units per time.