How to calculate production capacity
Every capacity figure is time × rate. The rate is the machine’s output per hour at its ideal cycle. What changes from one stage to the next is the time you count:
Output per hour = 3,600 ÷ ideal cycle time (s), or the machine’s rated output
Capacity = hours × output per hour × number of machines
| Capacity | Hours per machine in the period | What it shows |
|---|---|---|
| Design | calendar days × 24 h | the ceiling: the machine running nonstop, every day |
| Available | working days × shifts × hours per shift | what fits in your scheduled time |
| Effective | available − planned losses (breaks, changeovers, planned maintenance) | what you can make if everything goes to plan |
| Actual | (the output you enter) | what really came out |
With actual output you get the two ratios defined by Slack, Chambers and Johnston (Operations Management):
Utilization = actual output ÷ design capacity
Efficiency = actual output ÷ effective capacity
Some textbooks and plants use the words differently (for example, utilization against available rather than design capacity). Before comparing numbers with another site, check which definition each one uses.
How many machines or shifts demand calls for
Enter the period’s demand and the calculator shows:
Machines needed = round up (demand ÷ actual output per machine)
Shifts needed = round up (demand ÷ actual output per shift)
It uses actual output, not effective capacity, because actual output is what you can count on today. It also shows how many machines would do at 100% efficiency: the gap is what unplanned losses cost you in equipment.
Worked example
The values preloaded in the calculator describe 2 identical machines with a 45 second ideal cycle, in a 30 day month with 22 working days on 2 shifts of 8 hours:
- Output per hour = 3,600 ÷ 45 = 80 units/h per machine, 160 for both
- Design = 30 × 24 = 720 h × 160 = 115,200 units
- Available = 22 × 2 × 8 = 352 h × 160 = 56,320 units
- Planned losses per machine: 1 h of breaks per shift (22 × 2 × 1 = 44 h), 16 h of changeovers and 8 h of planned maintenance = 68 h
- Effective = (352 − 68) = 284 h × 160 = 45,440 units
- Actual = 36,000 units
- Utilization = 36,000 ÷ 115,200 = 31.3%
- Efficiency = 36,000 ÷ 45,440 = 79.2%
For a demand of 45,000 units in the month: each machine made 18,000, so you need 45,000 ÷ 18,000 = 2.5, that is 3 machines on the same 2 shifts. Or, with the 2 machines, 3 shifts (2.5 rounded up), which still fit in 24 hours. At 100% efficiency each machine would make 22,720 units and 2 machines would do.
How to read the result
- Low utilization is almost always calendar time with no shift: weekends, a third shift that does not exist. That capacity is bought with people, not machines. In the example, 31% utilization says there is room to grow without new equipment.
- Low efficiency is loss inside the shift that was not in the plan: breakdowns, minor stops, slow running and scrap. That is where the OEE calculator splits the losses apart, and the MTBF and MTTR calculator tackles breakdowns.
- The gap between available and effective is planned losses. Long changeovers take hours from every machine, every month. Quick changeover (SMED) gives those hours back.
- Before buying a machine, compare the two answers: if 100% efficiency would cover demand with the machines you have, attacking losses is cheaper. To put a price on each lost hour, use the downtime cost calculator.
Capacity efficiency and OEE
Both measure losses, but against different bases. OEE starts from planned production time and counts changeovers as an availability loss, because the machine could have been making parts. Capacity efficiency takes changeovers out of the base (they are a planned loss) and measures only what was lost outside the plan. So efficiency usually comes out higher than the same machine’s OEE. Use efficiency to plan capacity and OEE to go after losses, changeovers included.
Common mistakes
- Using the average cycle instead of the ideal cycle. The average already has losses built in, so efficiency lands near 100% without the machine being any good. Measure the ideal cycle with a time study.
- Adding up machines that work in series. On a line, capacity is the bottleneck’s, the slowest station. Work out each station and keep the lowest. To spread the work across stations, see line balancing and takt time.
- Ignoring the product mix. With products on different cycles, use the average of the ideal cycles weighted by each one’s volume, or work in hours instead of units.
- Planning on effective capacity. It assumes 100% efficiency. When you promise a date to a customer, use what the plant really delivers.