Open ten status reports and you’ll find at least three projects reporting a Cost Performance Index of exactly 1.00. On plan! Perfectly healthy! Except half of them are quietly on fire. A clean 1.00 is rarely a measurement — it’s a default, and defaults are where bad news goes to hide.
Earned value isn’t hard, but it is precise. Get the three inputs right and CPI/SPI become the most honest numbers on your dashboard. Get them wrong — or let a tool fake them — and you’ve built your steering committee a very confident lie.
The three numbers that matter
- BAC — Budget at Completion. What the whole project is authorized to cost.
- EV — Earned Value. How much of that budget the work actually done represents. Not hours burned — value delivered.
- AC — Actual Cost. What you’ve truly spent to get there.
From those: CPI = EV ÷ AC (above 1.0 = under budget) and SPI = EV ÷ PV, where Planned Value is how much you should have earned by now. Simple arithmetic — the danger is entirely in the inputs.
Where the fake 1.00 comes from
Most tools store CPI and SPI as fields that default to 1.0 and are never actually computed. A brand-new, empty project shows a flawless 1.00 — and because it’s green, nobody questions it. The number survives all the way to the executive briefing, right up until the overrun is undeniable.
The fix is a rule, not a formula: when the inputs for a metric are missing, show “—”, never 1.00. A dash prompts a question (“why don’t we have actuals yet?”). A fake 1.00 ends the conversation.
Earn value by task, not by vibe
A single project-level “percent complete” slider is easy to game — finish the cheap, easy tasks first and your number races ahead of reality. Cost-weighting fixes it: each task contributes its own cost, weighted by how complete it is. Clear the expensive, critical work and your earned value climbs honestly; clear the trivial stuff and it barely moves. A project that’s “80% done” but has only finished its cheapest tasks will — correctly — show a lower earned value.
Measure schedule against the plan you actually agreed to
SPI is only as honest as what it’s measured against. A flat calendar line spread evenly across start and end is better than nothing, but it assumes work arrives at a constant rate, which it never does. Measure against your baseline’s time-phased schedule and SPI finally reflects the plan your sponsor signed off on — the kind of number you can defend when someone pushes back.
The 60-second read
Next status meeting, run this on any green project: ask what its EV, AC and BAC are. If no one can answer, the 1.00 is decorative. Real earned value takes a budget, a baseline, and a little discipline about where “actual” comes from — and in return it tells you the truth early enough to do something about it.
See it in ProjexHQ
ProjexHQ computes CPI and SPI from your budget, task progress, baseline and logged time — and shows a plain “—” when the data isn’t there, never a fake 1.00.
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