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Foundation · 6 min read

Total float (and free float)

How far an activity can slip before the project finish moves — and why float is where schedules get gamed.

Working definition

Total float is the number of working days an activity can slip before it delays project completion. Free float is the smaller, stricter version: how far it can slip before it disturbs the very next activity. Float is the schedule’s shock absorber — and because whoever controls it controls the flexibility in the plan, it is the most contested quantity in schedule review.

Scope note

Float use and ownership are governed by the contract and applicable law. This guide explains schedule mechanics and common administration practices, not legal entitlement.

Key takeaways

  • Total float is a network output measured against a completion condition; it is not a fixed allowance owned by one activity or party.
  • Free float protects the immediate successor, while total float protects the controlling completion. Both are useful and answer different questions.
  • Track float movement and the input changes behind it. A restored float value is not automatically recovery.
01

Total float is shared flexibility in the network

Total float is the amount of time an activity may move before it affects the applicable late date or completion condition calculated by the schedule. In a simple unconstrained network that condition is usually project completion. In a real P6 file, constraints, multiple calendars, external relationships, and the selected scheduling options can shape the value. Treat total float as a result to interpret, not a field to read in isolation.

Float belongs to a path as much as it belongs to an activity. Several activities on the same chain may each display ten days of total float, but the path does not contain ten days for every activity independently. If the first activity consumes six days, the downstream activities on that unchanged path will generally inherit the reduced flexibility. Adding the displayed values would count the same time repeatedly.

02

Total float and free float answer different questions

Total float asks how much an activity may move before the controlling completion condition is affected. Free float asks how much it may move before delaying the early start of an immediate successor. An activity can have positive total float and zero free float: completion remains protected, but the next trade or handoff is disturbed as soon as the activity slips.

Owners and contractors need both views. Total float is central to completion forecasting and time-impact analysis. Free float helps expose local disruption, crew-interface risk, and whether a near-term commitment can move without forcing a resequence. Neither number by itself proves responsibility or entitlement.

03

Why float values differ across calendars and settings

P6 stores and calculates time at a finer resolution than the rounded day values commonly displayed. A result shown as five days depends on the hours-per-day conversion and the calendars used by the activities and relationships. Two activities that both display five days can therefore represent different working-time quantities.

The project’s late-date calculation also matters. A required finish constraint can create negative float; removing or moving that constraint can restore float without changing the work. Scheduling a project by itself can treat external relationships differently than scheduling it with related projects. A defensible float comparison records the units and settings instead of copying two rounded values into a spreadsheet and treating the difference as self-explanatory.

04

Who may use float is a contract question

Many contracts describe float as a project resource available to whichever party legitimately uses it first. Other contracts reserve float, allocate it, require shared use, or address specific categories such as weather allowance and owner review time. Silence does not create a universal rule. The schedule analyst should describe who consumed time and what the network effect was; counsel and the contract determine the legal consequence.

Good administration makes float use visible while options still exist. If an owner review consumes a path’s remaining flexibility, record the dates, required duration, actual duration, notice, and effect. If contractor resequencing consumes the same float, record that too. Waiting until the path is negative turns a manageable coordination issue into a retrospective allocation dispute.

05

Float consumption is an early-warning system

Completion dates often remain unchanged while float is being spent. A path that falls from thirty days to eight has experienced significant deterioration even if the contractual milestone still prints the same date. Tracking float by path and work area between updates reveals that deterioration before it reaches zero.

The explanation matters more than the arithmetic. Float can decline because work progressed slower than planned, a successor duration increased, logic tightened, a calendar changed, or another path became controlling. It can increase because work outperformed, an approved resequence shortened the chain, or schedule inputs were loosened. Review the change log before labeling the movement either good or bad.

06

Negative and unusually high float

Negative float means the calculated network cannot meet an imposed late date or required finish under the current inputs. The magnitude is useful, but the root condition must be identified: genuine performance delay, a stale constraint, a calendar mismatch, or an external interface can all produce it. A recovery plan should explain how the negative value will be reduced through executable changes, not merely move the constraint.

Very high positive float may be legitimate on optional or distant work, but it often points to weak logic, a missing successor, or a completion milestone that does not capture the activity’s real obligation. Review the distribution and the tails. A schedule whose middle looks reasonable can still hide major network defects in a small number of extreme values.

Worked example

Illustrative float burn across two updates

A utility-relocation path has 20 workdays of total float in the January update. During February, field production loses six days and a required agency review is forecast four days longer. No logic or calendar changes are approved.

  1. The path would be expected to lose roughly ten workdays of flexibility, subject to recalculation against the rest of the network.
  2. If the February file instead shows 22 days of float, compare logic, calendars, constraints, and remaining durations before accepting the apparent improvement.
  3. A deleted successor or moved completion constraint can restore displayed float without recovering a single day of physical work.
The review conclusion should state both the measured float movement and the input changes that caused it. “Float improved by two days” is not sufficient on its own.

Field-ready control

Float review checklist

  • Confirm the project, milestone, data date, time units, calendars, and scheduling options being compared.
  • Compare float by path and work area, not only by individual activity.
  • Identify the largest positive and negative changes since the prior accepted update.
  • Reconcile each material change to progress, duration, logic, calendar, or constraint changes.
  • Review free float where immediate handoffs and trade interfaces matter.
  • Apply the project’s actual contract language before making any ownership or entitlement conclusion.

Common questions

Can total float be added across activities?

Usually no. Activities on the same path often display the same shared flexibility. Adding those values counts the same path float multiple times.

Is negative float the same as project delay?

It shows that the calculated network misses an imposed late condition, but the analyst must identify the condition and its cause. An obsolete constraint can create negative float just as real performance delay can.

Does positive float mean an activity can be ignored?

No. The activity may carry safety, cost, procurement, local-interface, or future path risk. Float measures schedule flexibility under the current model, not management importance.

Sources and scope

Follow the reference trail.

This guide is original educational commentary. Kairos reference records identify the source organizations, editions and scope behind this guidance. The original publishers retain their publications and rights.

10S-90: Cost Engineering TerminologyAACE International · checked 2026-08-01Scheduling projectsOracle · checked 2026-08-01Schedule Assessment Guide: Best Practices for Project SchedulesU.S. Government Accountability Office · checked 2026-08-01Delay and Disruption Protocol, second editionSociety of Construction Law · checked 2026-08-01