How do you calculate mold parts per hour?

Multiply shots per hour by cavities. Shots per hour is 3600 divided by cycle time in seconds. With a 30-second cycle (120 shots/hr) and 4 cavities, capacity is 120 x 4 = 480 parts per hour, or 4,800/hr at the gross uptime in this example.

How do I convert cycle time to shots per hour?

Divide 3600 (seconds in an hour) by the cycle time in seconds. A 30-second cycle gives 120 shots/hr; a 20-second cycle gives 180 shots/hr. Shaving cycle time is the fastest lever on output.

What is a good parts-per-hour number for injection molding?

There is no universal target — it depends on part size, resin, and cavitation. The useful test is whether your capacity comfortably exceeds target demand. Here, 4,800 parts/hr of good capacity against 1,000 parts/hr of demand means one press easily covers the order.

Does this calculator account for downtime and scrap?

The gross capacity figure does not. It is the theoretical ceiling. To get realistic output, multiply by your OEE (availability x performance x quality), which is why the example shows good output below gross capacity.

More cavities or faster cycle — which raises output more?

Both scale linearly, so doubling cavities or halving cycle time both double capacity. Cavities cost tooling money up front; cycle reduction costs process development time. Run both scenarios before committing the mold design.

How many cavities do I need for my annual volume?

Divide annual demand by (shots per hour x available production hours per year x your yield), then round up to the next practical cavitation. Validate the resulting cycle time and clamp tonnage are achievable on your press.

Injection Molding calculator

Mold Parts Per Hour Calculator

Mold parts per hour tells you how many good parts a single injection molding tool can produce in an hour by multiplying shots per hour by the number of cavities. Process engineers, production planners, and tooling buyers use it to size molds, confirm a press can hit a delivery date, and decide whether a 4-cavity tool is enough or you need an 8- or 16-cavity build. It is the single most important capacity number behind every molding quote and machine-loading schedule. Get it wrong and you either overbuy tooling or miss the shipment.

What this calculator does

Calculate parts per hour output from cycle time and mold cavitation to plan production capacity and press scheduling.
Use this when scheduling press time, quoting delivery dates, or comparing output rates between mold configurations. Helps determine if a mold can meet hourly or shift targets.
It computes hourly good-part capacity as shots per hour multiplied by cavities, then compares that capacity against your target demand.

Formula used

Capacity per hour = Shots per hour x Cavities
Utilization = Target demand / Capacity per hour

Inputs explained

Parts needed per hour (target demand):
Shots per hour (3600 / cycle time in seconds):
Number of cavities in the mold:

How to use the result

Use it when quoting a new part, validating that a cycle time hits the required annual volume, or deciding how many cavities to cut into a new mold.
It assumes 100% uptime and zero scrap in the gross figure; real-world output is lower once you apply OEE and reject rates, so treat the capacity number as a theoretical ceiling.

Current U.S. benchmarks

The producer price index for plastic resins and materials stands at 319.371 (BLS, May 2026), up 19.5% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 9,635 plastics product manufacturing establishments employing about 677,302 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate mold parts per hour? Multiply shots per hour by cavities. Shots per hour is 3600 divided by cycle time in seconds. With a 30-second cycle (120 shots/hr) and 4 cavities, capacity is 120 x 4 = 480 parts per hour, or 4,800/hr at the gross uptime in this example.
How do I convert cycle time to shots per hour? Divide 3600 (seconds in an hour) by the cycle time in seconds. A 30-second cycle gives 120 shots/hr; a 20-second cycle gives 180 shots/hr. Shaving cycle time is the fastest lever on output.
What is a good parts-per-hour number for injection molding? There is no universal target — it depends on part size, resin, and cavitation. The useful test is whether your capacity comfortably exceeds target demand. Here, 4,800 parts/hr of good capacity against 1,000 parts/hr of demand means one press easily covers the order.
Does this calculator account for downtime and scrap? The gross capacity figure does not. It is the theoretical ceiling. To get realistic output, multiply by your OEE (availability x performance x quality), which is why the example shows good output below gross capacity.
More cavities or faster cycle — which raises output more? Both scale linearly, so doubling cavities or halving cycle time both double capacity. Cavities cost tooling money up front; cycle reduction costs process development time. Run both scenarios before committing the mold design.

Last reviewed 2026-05-12.