How much capacity do you already own?

Capacity questions usually arrive as “do we need another machine?”. This works out what the machines you have would produce if you got more of their time, which is the cheaper answer and usually the right one.

Gross hours are simply machines × hours per day × days × weeks. That is the time you are already paying for.

Changeover is taken off before utilisation, because it is real work rather than lost time. Every batch costs one changeover, so the per-unit overhead is changeover ÷ batch size. Halving batch sizes without touching setup time quietly removes capacity — you can see that here by changing the batch figure.

Utilisation is the share of remaining time the machine actually spends cutting. It covers breakdowns, waiting for material, waiting for an operator, waiting for a decision, and running slow. Most factories that have never measured it land between 50% and 65%, which is why the gap between the two bars is normally larger than anyone expects.

This is a single-stage model. If your product crosses several work centres, run the bottleneck — the rest of the line cannot go faster than that anyway.