OEE Calculator — Overall Equipment Effectiveness

• Availability = Running time ÷ Planned production time — was the machine on, or stopped for breakdowns and changeovers?
• Performance = (Ideal cycle time × Total pieces) ÷ Running time — how close to rated speed you actually ran, once it was on.
• Quality = Good pieces ÷ Total pieces produced — of what came off the line, how much was sellable?

Each factor isolates a different failure mode. A machine can run 95% of the time (high Availability) and still have poor OEE if it runs slow or scraps parts — which is why the three are multiplied, not averaged.

An 8-hour shift (480 minutes) is planned. The line actually ran for 440 minutes. At a 1-minute ideal cycle time, it produced 400 pieces, of which 380 passed inspection.

Try these exact numbers in the calculator above to see how changing any one factor moves the final score.

Nakajima's six big losses map directly onto the three OEE factors — each one has two loss categories:

• Availability losses: breakdowns, and planned stops (changeovers, setups)
• Performance losses: minor stoppages, and running below rated speed
• Quality losses: defects and rework, and startup/yield losses

For most plants, Availability is where the biggest OEE losses sit — and it's built from the same two numbers that drive MTBF and MTTR. A rising MTBF and falling MTTR both push Availability — and therefore OEE — up. Run those numbers first if you want to know what's actually causing the loss, or jump straight to the Availability calculator.