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Scheduling

Duration

In Plain English

The number of days or hours it takes to complete a scheduled task.

Definition

Duration is the estimated or actual calendar time required to complete a scheduled activity, measured in work days, calendar days, or hours depending on the project calendar. Duration is calculated based on the quantity of work, production rates, crew size, and available resources. Activity durations are the primary input to CPM schedule calculations.

Why It Matters in Bidding

Activity durations are the raw input to every CPM schedule, so the accuracy of a bid's proposed schedule—and the general conditions cost tied to it—depends on realistic durations built from production rates and crew sizes. Underestimating durations to win on schedule can backfire, since it inflates liquidated-damages exposure and understates the general conditions and supervision the estimator should have carried.

Example

An estimator derives the slab-on-grade duration by dividing 60,000 SF by a placing crew's daily production rate, lands on eight working days, and feeds that into the CPM schedule that sets project general conditions for the bid.

Related Terms

Critical PathFloatResource LevelingSchedule Compression

Frequently Asked Questions

Duration is the work quantity divided by the crew's production rate, adjusted for crew size, shifts, and the project calendar. For example, total square footage divided by daily output yields work days. Estimators also factor weather, learning curve, and resource availability rather than relying on a single optimistic number.
Longer durations extend general conditions, supervision, equipment rental, and overhead that accrue per day, so duration directly scales time-related costs. An unrealistically short schedule understates these costs and increases liquidated-damages risk if the team cannot deliver, making honest duration estimating a margin-protection exercise, not just a scheduling one.
Effort is the total labor hours required, while duration is the calendar time to complete the activity. Adding crew can shorten duration without changing total effort, up to a point of diminishing returns. Estimators balance the two to hit a target finish date while keeping labor productivity and cost in check.

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