Parts Per Hour Calculator

Calculate theoretical injection molding parts per minute and hour from cycle time and active cavities. This practical tool is an engineering estimate—validate decisions against machine, material, mold, and process data.

Formula and method

Theoretical parts per hour = 3,600 ÷ cycle time × active cavities.

Inputs and units

Enter the measured mold-to-mold cycle in seconds and the number of cavities that produce a part on every cycle. Use a stopwatch, machine cycle record, or the Cycle Time Calculator for the time; use the current mold setup for active cavities.

Worked example

3,600 ÷ 30 s × 4 active cavities = 480 parts/hour (8 parts/minute from 120 cycles/hour).

Start with a stable, defined cycle

Measure one complete mold-to-mold cycle, including fill, pack, cooling, mold motion, ejection, and any automation that controls the next cycle. Use the Cycle Time Calculator when those steps must be assembled.

Count active cavities, not nominal positions

Enter only cavities actually producing parts on every cycle. A blocked or disabled cavity does not contribute to parts per cycle, even if it remains in the mold layout.

Keep theoretical and effective output separate

This tool reports the continuous mechanical rate. Apply time loss with Machine Utilization or OEE Capacity, quality loss with Scrap-Adjusted Output, and shift duration with Parts Per Shift.

Interpretation, assumptions, and limitations

The rate assumes uninterrupted cycling at the entered time and one part from every active cavity on every cycle. It excludes planned and unplanned downtime, microstops, speed loss, startup loss, rejected parts, and downstream constraints.

FAQ

Is this actual good-part output?

No. It is the theoretical rate at the entered cycle and active-cavity count. Downtime, slower running, and rejects require separate measured assumptions.