Project hitches are inevitable, regardless of experience. Even the most well-crafted plans encounter unexpected roadblocks and delays, jeopardizing successful completion.
But incorporating a time buffer, known as a float in project management, can guard against these uncertainties, enabling on-time delivery without the pressures of tight deadlines and overwork.
What’s float in project management?
Every project has interdependent tasks. If work on one item stalls, it can delay the completion of others and impede final product delivery in a worst-case scenario.
To prevent minor delays from disrupting the entire project, project managers integrate floats into their timelines. By providing a buffer for unexpected setbacks, schedule floats offer teams flexibility to effectively handle small delays and project challenges without negatively affecting dependent work or compromising the project’s timely completion.
In scheduling, project managers often use floats alongside the critical path method (CPM) to determine the necessary project completion time. CPM is a technique that identifies the longest stretch of dependent activities in a project schedule, highlighting the most critical tasks that directly impact the timeline. But regardless of your chosen project management framework — whether Kanban, Scrum in agile methodologies, or Waterfall — integrating floats into timelines is universally applicable.
5 different types of floats
Different float types cater to specific needs in project scheduling. While one might provide team members with clear deadlines for task completion, another assists project managers in tracking progress. These float variations enable tailored management approaches, enhancing your project execution’s efficiency and effectiveness.
1. Total float
Total float (TF) measures the maximum delay possible for an activity without affecting the project’s completion date. It’s a key metric for project managers to evaluate how individual task timelines impact overall delivery, helping to identify critical tasks and plan buffer times efficiently.
To calculate TF, subtract the earliest start or finish dates from the latest ones.
Formula 1: TF= Latest start date (LS) – Earliest start date (ES)
Formula 2: TF = Latest finish date (LF) – Earliest finish date (EF)
2. Free float
Free float in project management (FF) quantifies the time leaders can delay starting a task without causing subsequent delays, evaluating the impact of a task’s timing on its immediate successor rather than the entire project.
To calculate FF, subtract the current task’s early finish date from its dependent task’s early start date.
Formula: FF = Early start (ES) of dependent task – Early finish (EF) of current task
TF and FF are the most frequently used calculations in project management. While not as common, the Project Management Book of Knowledge (PMBoK) outlines three additional slack types. Understanding each one is crucial for those seeking Project Management Professional (PMP) certification, since they’re all critical components of the exam.
3. Project float
Project float (PF) becomes key when clients set strict deadlines for project completion that businesses must meet. Project leaders typically plan delivery before the drop-dead date, or final due date, to manage this, creating a buffer against potential delays. PF measures this slack, focusing on the client’s expected delivery date instead of the project manager’s internal competition target.
Leaders calculate PF using a formula similar to TF. But, while TF relates to individual tasks, PF pertains to the entire project’s completion timeline. The calculation involves subtracting the earliest planned completion date from the client-imposed deadline.
Formula: PF = Latest (imposed) finish date (LF) – Earliest (planned) finish date (EF)
4. Interfering float
Project managers calculate interfering float (INTF) to assess how much they can delay a specific task without affecting the client’s delivery date. This involves taking the task’s TF and subtracting its FF, considering the client-imposed deadline.
Formula: INTF = TF – FF
5. Independent float
The independent float (INDF) gauges how long project managers can delay a task without affecting the earliest start time of its dependent activity. Since this slack type doesn’t impact the project’s earliest finish (EF) date, it’s considered independent.
To calculate INDF, subtract the early start (ES) of the successor task from the late finish (LF) of the preceding activity.
Formula: INDF = Early start (ES) of dependent task – (Late finish (LF) of current task + Duration of current task)
The importance of float in project management
Incorporating floats is crucial in project management, helping to:
- Monitor progress: Integrated with time tracking, floats provide project managers with clear progress perspectives. This combination helps teams identify lagging tasks and understand a delay’s impact on dependent activities, facilitating better timeline and expectation management.
- Boost productivity and efficiency: Float helps establish the project roadmap. They enable project managers to adjust task sequences with slack during planning, ensuring key activities stay on track and preventing oversights.
- Identify priorities: Using float as a prioritization tool enables teams to defer tasks with more slack, focusing first on completing those with little to no float.
- Boost morale: Floats offer a clearer view of project timelines, enabling project managers to reallocate resources and fast-track certain tasks during crunch times. This approach helps teams meet tight deadlines and improves morale by reducing the stress and workload of stringent timelines.
How to calculate float in project management: A step-by-step guide
Float calculation isn’t complicated, but it does require initial groundwork. Understanding each task’s details, interrelationships, and impact on the timeline is key to applying floats for flexibility and efficiency. Here’s a three-step guide to calculating and utilizing floats effectively.
1. Understand the project workflow
Visually map out project tasks by completion order using a network diagram to help the team identify dependencies. Then, transfer this information to a Gantt chart or project roadmap in your preferred project management tool, noting each activity’s projected earliest start date and duration. If the first activity in the chain has an early start (ES) of zero and takes three days to complete, its earliest finish (EF) and successor task EF are both three.
Next, calculate each task’s latest start and finish and include this in the Gantt chart and roadmap. If you initially plan to start the first activity on day zero and finish on day three but then decide to delay its start by two days, the latest start (LS) becomes day two. Consequently, the task’s completion, or its latest finish (LF), would shift to day five, assuming it still requires the same duration.
Some tasks will have no flexibility regarding start dates, so they have no float. Note these tasks, as they’re important for the next step in managing the project’s timeline.
2. Identify paths
Revisit the network diagram and identify which activities depend on the completion of others before they can commence and which have no float. These are critical tasks, with the longest sequence of dependent successors forming the critical path and the time required to complete this sequence dictating the overall project timeline. Team members can work on non-critical and independent tasks alongside the critical path activities, effectively using resources and time for efficient project execution.
3. Calculate float
After mapping out the project workflow and identifying key tasks along the critical path, you now have the necessary information to calculate the project, total, and free float using these formulas:
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Project float: Subtract the earliest time to complete the critical path from the project’s expected duration and deadline date. This number indicates the maximum delay for starting the critical path without affecting the overall project timeline.
Formula: Project float (PF) = Latest (imposed) finish date (LF) – Earliest (planned) finish date (EF)
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Total float: Calculate each task’s total float or the maximum time you can delay a task without impacting the project’s end date by subtracting its earliest start date from its latest finish date. Document these calculations in your project management software for easy reference and tracking.
Formula 1: Latest start date (LS) – Earliest start date (ES)
Formula 2: Latest finish date (LF) – Earliest finish date (EF)
- Free float: Calculate the free float for a sequence of dependent tasks by subtracting the earliest finish date of the current task from the next task’s earliest start date. Remember, a task’s free float, representing the delay allowance without impacting the next task, can’t be more than its total float, as free float only measures the delay allowance without affecting subsequent tasks.
Formula: Free float (FF) = Early start (ES) of dependent task – Early finish (EF) of current task
Example of float in project management
Imagine you work for a website development company, and your latest project requires uploading to the client’s server in six weeks (30 working days). To meet the client’s deadline, your team must complete several tasks:
- Create the website’s wireframe
- Develop the backend
- Design graphics
- Populate the site with content
- Upload to the server
Backend programming and graphics development can’t start until the design team finalizes the wireframe. You’ve allocated eight days for wireframing, but the team can finish it in six, creating a float of two days. If there are any hiccups, you can delay starting the backend and graphic work by up to two days without affecting the final delivery date. This float provides a cushion for unexpected challenges in the early project stages.
Successful project management with Tempo Strategic Roadmaps
Tempo Strategic Roadmaps is an indispensable tool to help you calculate floats in project management. Using Jira-enabled Strategic Roadmaps with project management software helps your team quickly visualize dependent activities and establish the project’s critical path. Once complete, you can prioritize tasks and build team alignment behind the execution plan.
No matter your industry, be it IT, product development, or project management, you can work smarter with Strategic Roadmaps.
