OEE Calculator: Turn Shift Data Into a Real Number You Can Trust

The problem this kills

Everyone in the plant has an opinion about which machine is the bottleneck, whether the night shift is "slower," and how much the changeovers are really costing you. The opinions are loud, confident, and usually unprovable — because the only number anyone has is "it felt busy" or "we made our count, I think." So improvement meetings turn into who-can-talk-loudest, and the same chronic losses survive another quarter because nobody can size them.

OEE — Overall Equipment Effectiveness — is the one number that settles it: how much good product a machine actually made versus what it could have made if it ran perfectly the whole planned time. But OEE has a reputation for being either a black box in a six-figure MES, or a fragile spreadsheet where one person fudges "planned time" and the whole number lies. The fix isn't a bigger system. It's a small, honest tool that defines planned time and ideal rate carefully, shows you the three losses underneath the headline, and won't publish a shift until a human has looked at it. You can build that yourself.

What you'll build

A logged-in web tool for your floor. For each machine + shift + date you enter (or import from a CSV/Sheet) the handful of inputs OEE needs: planned production time, downtime, the machine's ideal cycle time or rate, the total count it made, and the good vs scrap split. The tool computes the three factors — Availability (was it running when it should have been?), Performance (did it run at its ideal speed?), and Quality (how much was good?) — and multiplies them into OEE. Crucially, it shows you each factor and each loss, not just the product, so you can see whether you're losing to downtime, speed, or scrap. Then the supervisor reviews and approves the shift, and only approved shifts join the OEE history that feeds the trend chart and the export.

What's inside the Implementation Plan

The downloadable plan is a step-by-step file you paste into an AI coding agent. It opens by interviewing you about your plant — your real machines, your shift pattern, and (the part that makes or breaks OEE) exactly how you define planned production time and each machine's ideal cycle time or rate, plus how you count downtime and classify scrap. It reads a short spec back to you for a thumbs-up, then builds the calculator around your definitions instead of a generic template. From there it walks the agent through the data model, the data-entry and CSV-import screens, the OEE math with each factor shown, the supervisor approval gate, the history + trend, and the CSV export. Every step ends with a ready-to-copy prompt.

The governance it includes (this is the point)

This isn't a throwaway spreadsheet. The plan builds in the controls a real operation needs: login so only your team can use it, row-level security so a plant or site only ever sees its own data, and a complete audit trail of every entry, edit, and approval — who, what, and when. The human gate is the heart of it: a shift's OEE is drafted from the inputs but is never published to the official history until a named supervisor reviews the inputs and outputs and approves it — and once published, edits are blocked or require a re-approval, so the history you report from can't quietly change. And a duplicate guard keyed on machine + shift + date stops the same shift from being entered or imported twice and double-counting your numbers.

Who it's for

Plant managers, continuous-improvement leads, and shift supervisors who are tired of debating performance from gut feel and want one number — and the three losses underneath it — that everyone can trust. If you can describe how your plant defines a machine's planned running time and its ideal rate, you can build this.

You've got this — open the plan, paste the first prompt, and you'll be computing your first real, approved OEE this weekend.