Free calculator
Earned schedule calculator: ES, SV(t) and SPI(t)
Paste the cumulative planned value for each period, then enter the earned value and how many periods have passed. You get the earned schedule, the time variance, SPI(t) and a forecast duration.
Calculator
The formulas
| ES = C + (EV − PVC) / (PVC+1 − PVC) | C is the last whole period where planned value was at or below today's EV |
|---|---|
| SV(t) = ES − AT | schedule variance in time: negative means behind |
| SPI(t) = ES / AT | schedule performance in time |
| IEAC(t) = PD / SPI(t) | forecast duration, where PD is the planned duration |
Worked example
A ten-month project plans a cumulative value of 100, 220, 360 and 520 in its first four months. At the end of month 4 the earned value is 400.
The plan reached 360 at month 3 and 520 at month 4, so C is 3 and ES = 3 + (400 − 360) / (520 − 360) = 3.25 months. SV(t) is 3.25 − 4 = −0.75 months, and SPI(t) is 3.25 / 4 = 0.81. At that pace the project takes 10 / 0.8125 = 12.3 months.
The earned schedule guide explains why this is more reliable than SPI late in a project.
Common questions
Why not just use SPI?
SPI is EV / PV in money, and it returns to 1.0 at the end of every project, late or not. SPI(t) measures time, so it stays meaningful to the last day.
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