OEE is the most widely used single number for how well a machine is used. This page gives the short answer; the full OEE guide covers the six big losses, benchmarks and how to raise it on a CNC floor.
The OEE formula
OEE = Availability × Performance × Quality. Each factor catches a different kind of loss:
Availability
- Formula
- Run time ÷ planned production time
- Loss it catches
- Stops and breakdowns
Performance
- Formula
- (Ideal cycle time × total parts) ÷ run time
- Loss it catches
- Running slower than ideal
Quality
- Formula
- Good parts ÷ total parts
- Loss it catches
- Scrap and rework
| Factor | Formula | Loss it catches |
|---|---|---|
| Availability | Run time ÷ planned production time | Stops and breakdowns |
| Performance | (Ideal cycle time × total parts) ÷ run time | Running slower than ideal |
| Quality | Good parts ÷ total parts | Scrap and rework |
A machine at 100% OEE made only good parts, at its ideal speed, with no stops during planned time.
A worked example
One machine, one shift (illustrative numbers):
Availability
- Value
- 380 min run ÷ 420 min planned = 90.5%
Performance
- Value
- (60 s ideal × 340 parts) ÷ 22,800 s run = 89.5%
Quality
- Value
- 330 good ÷ 340 total = 97.1%
| Factor | Value |
|---|---|
| Availability | 380 min run ÷ 420 min planned = 90.5% |
| Performance | (60 s ideal × 340 parts) ÷ 22,800 s run = 89.5% |
| Quality | 330 good ÷ 340 total = 97.1% |
OEE = 90.5% × 89.5% × 97.1% ≈ 78.6%. Try your own shift in the OEE calculator, which shows each step of the maths.