FIELD NOTES
What is CPI in Construction and Why It Matters
The one number that tells you if your project will finish on budget.
The Short Answer
CPI stands for Cost Performance Index. It measures how efficiently your labor is being used on a construction project. A CPI of 1.0 means you're exactly on budget. Above 1.0 means you're doing better than planned. Below 1.0 means you're spending more than you should.
CPI = Earned Value / Actual Cost
Why Construction Needs CPI
According to FMI's 2025 Project Management Study, only 2.5% of construction firms report that projects consistently finish on time and on budget. That's not a quality problem. It's a visibility problem.
Most contractors don't know they're over budget until the job is done. By then, the margin is gone. CPI changes that. It tells you during the project whether your labor is productive enough to finish on budget.
How CPI Works in Practice
Imagine you budgeted 240 hours for copper pipe installation. After two weeks, your crew has worked 96 hours and installed 177 linear feet out of a 2,000 LF scope.
Percent complete: 177 / 2,000 = 8.85%
Earned hours: 240 × 8.85% = 21.24 hours
CPI: 21.24 / 96 = 0.22
A CPI of 0.22 means for every hour your crew works, they're only producing 0.22 hours of value. At this rate, the 240-hour budget will take over 1,000 hours to complete. That's the kind of insight you need now, not at job closeout.
The Three States of CPI
Your crew is outperforming the budget. Earned value exceeds actual cost.
Spending slightly faster than earning. Time to investigate before it gets worse.
Significant overrun. Every additional hour deepens the loss unless you intervene.
CPI's Superpower: Projection
The real value of CPI isn't knowing where you are. It's knowing where you're going.
Estimate at Completion (EAC) = Budget / CPI
If your budget is 240 hours and your CPI is 0.85, your projected total is 240 / 0.85 = 282 hours. You'll overshoot by 42 hours unless something changes. That projection updates automatically with every daily log, giving you a living forecast instead of a static budget.
How to Start Tracking CPI
You need three things for each cost code:
- Budgeted hours from the estimate
- Actual hours logged daily by field crews
- Quantity installed to calculate percent complete
From those inputs, CPI computes automatically. The challenge isn't the math. It's getting consistent daily data from the field without creating friction for your crews. That's exactly what UnitPace solves.
Start tracking CPI on your next project.
UnitPace makes it simple. Foremen log from the field, you see CPI instantly.
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