# Construction Schedule Float Calculator

> Calculate an activity’s total float and free float from its early start, duration, late finish and the earliest start of its successors.

Category: Construction · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/construction-schedule-float-calculator

Total float is how long an activity can slip without delaying the project; free float is how long it can slip without delaying the next activity. Both come from the critical path dates.

Also called: Total float calculator, Free float calculator.

## Inputs
- Early start (ES) (unit day; default 10)
- Duration (unit days; default 5)
- Late finish (LF) (unit day; default 20)
- Earliest early start of successors (unit day; default 17)

## Results
- Total float
- Free float
- Early finish (EF)
- Late start (LS)
- Status

## Formula

```
EF = ES + Duration;  LS = LF − Duration;  Total float = LF − EF = LS − ES;  Free float = ES(successor) − EF
```

Where:
- ES, EF: early start and finish from the forward pass
- LS, LF: late start and finish from the backward pass

## Worked example
1. EF = 10 + 5 = 15; LS = 20 − 5 = 15.
2. Total float = 20 − 15 = 5 days.
3. Free float = 17 − 15 = 2 days.

**Result:** The activity can slip 2 days without affecting its successor and 5 days without delaying the project.

## What the result means

Activities with zero total float are on the critical path. Negative float means the schedule already misses a required date and needs recovery.

## Assumptions and limits
- Finish-to-start links with no lag.
- Day numbers use the convention that an activity starting at ES finishes at ES + duration.
- Covers one activity; it does not compute the network’s forward and backward passes.

## Questions

### Who owns the float?

It depends on the contract. Many contracts say float belongs to the project, which affects delay claims.

### Can free float exceed total float?

No. Free float is always less than or equal to total float.

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_Quantities are estimates. Confirm requirements with your engineer or supplier before ordering materials._

Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/construction-schedule-float-calculator