Production Capacity Calculator
Turn cycle time and available hours into realistic capacity.
Capacity per month
18,360
- Capacity per day
- 835 units
- Capacity per shift
- 417 units
- Theoretical capacity per shift Before the efficiency factor — the physical ceiling.
- 491 units
Nameplate capacity is a number in a brochure. The capacity you can actually promise a customer is smaller, because it has to survive changeovers, breakdowns, breaks and defects. This calculator starts from the physical limit set by cycle time and then applies an efficiency factor, so the answer you get is the one you can defend in a planning meeting.
The three-level output — per shift, per day, per month — is deliberate. Capacity problems usually appear at the monthly level while being invisible at the shift level: a line that comfortably clears its shift target can still miss a monthly commitment because of changeover frequency, weekend gaps and maintenance windows. Enter the calendar you actually run, not the one in the standard cost model.
How the result is calculated
Capacity per shift = (Available minutes × 60 ÷ Cycle time) × Efficiency- Theoretical units per shift = Available seconds ÷ Bottleneck cycle time
- Effective units per shift = Theoretical units × Efficiency
- Capacity per day = Effective per shift × Shifts per day
- Capacity per month = Capacity per day × Production days
Variables
| Symbol | Meaning | Unit |
|---|---|---|
C | Capacity | units |
Ta | Available minutes per shift | min |
CT | Bottleneck cycle time | sec/unit |
E | Efficiency or OEE | % |
Worked example
A two-shift line has 450 available minutes per shift, a bottleneck cycle time of 55 seconds and a measured OEE of 85%. It runs 22 days a month.
- Theoretical per shift = (450 × 60) ÷ 55 = 27,000 ÷ 55 = 490.9 units
- Effective per shift = 490.9 × 0.85 = 417.3 units
- Per day = 417.3 × 2 = 834.6 units
- Per month = 834.6 × 22 = 18,361 units
Monthly capacity is about 18,360 units. Note the gap against the theoretical figure of 21,600 — the 15% efficiency factor removes roughly 3,240 units a month, which is the real cost of downtime and defects expressed in output rather than percentages.
What this calculation does not cover
- The bottleneck cycle time must be the slowest station. Using the average cycle time across a line overstates capacity by the amount of imbalance in the line.
- A single efficiency factor cannot separate downtime from speed loss or defects. If you need to know which one to attack, run the OEE calculator to split the losses.
- Capacity here is capacity for one product at a fixed cycle time. Mixed-model production with frequent changeovers needs a separate changeover allowance, or the monthly number will be optimistic.
- This is equipment capacity, not labour capacity. If staffing, tooling or material supply limits output before the machine does, the constraint is upstream of this model.
Frequently asked questions
Should I use OEE or plain efficiency as the factor?
Use OEE if you measure it, because it accounts for downtime, speed loss and defects together. Use a plain efficiency figure only when you have no OEE data — in that case pick a conservative value such as 75–80% rather than an optimistic one, since unmeasured efficiency is almost always worse than assumed.
How do I calculate capacity for a mixed-product line?
Calculate capacity separately for each product family using its own cycle time, then apply the planned production days allocated to each family. Summing a blended average cycle time across products with very different work content produces a capacity figure that is wrong for every product individually.
Why is my calculated capacity higher than what we actually ship?
The usual culprits, in order: cycle time taken from the average rather than the bottleneck station, efficiency assumed rather than measured, changeover time not reflected in production days, and material or labour constraints that stop the machine before its own capacity limit. Compare a week of actual output against this figure to see which one dominates.