What makes lights-out capacity different from a staffed batch?

The machine works without anyone on site, so a single unmonitored stop can burn the rest of the window. That is why the unattended uptime input usually sits well below the uptime you see during a staffed shift.

How many cycles can an overnight window hold?

Multiply the hours between the last operator leaving and the first returning by the cycle rate, then derate for tool changes and planned stops. Enter the cycles you trust the machine to start unattended.

Which loss should I fix first for a lights-out run?

Start with uptime. An unattended stop removes every remaining cycle in the window, while a yield loss removes only the parts from cycles that did run. Monitoring, tool-life limits, and safe park moves protect the window.

Does the target change the capacity result?

No. The target good-parts figure is a plan to compare against, not part of the calculation. The gap to target row shows the difference, and the verdict warns when the window falls short.

CNC Machining calculator

Lights-Out Machining Capacity Calculator

Unstaffed hours only pay off when the machine keeps cycling and the parts come off good. Multiply unattended parts per cycle by the lights-out cycles, then remove the shares lost to stopped time and to scrap.

What this calculator does

Estimate good parts an unattended run can produce after downtime and first-pass yield losses.

Formula used

Gross capacity = unattended parts per cycle × lights-out cycles
Downtime loss = gross capacity × (100 − unattended uptime) ÷ 100
Scrap loss = (gross capacity − downtime loss) × (100 − lights-out yield) ÷ 100
Good capacity = gross − downtime loss − scrap loss; yield = good ÷ gross × 100
Gap to target = good capacity − target good parts

Inputs explained

Unattended Parts per Cycle: Parts the fixture yields each unattended cycle.
Lights-Out Cycles: Cycles available while the shop is unstaffed.
Unattended Uptime: Share of unattended cycles the machine runs.
Lights-Out First-Pass Yield: Share of unattended parts good before rework.
Target Good Parts: Good parts the lights-out window should deliver.

How to use the result

Best suited to sizing an overnight unattended run, justifying in-process monitoring, planning the morning unload.
Chip, tool, and coolant failures not covered by monitoring end the run. Loading the magazine for the window is outside the cycle count.

Current U.S. benchmarks

The producer price index for steel mill products stands at 381.162 (BLS, Aug 2026), up 23.4% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 17,154 machine shops establishments employing about 223,303 workers (Census County Business Patterns, 2023).

Common questions

What makes lights-out capacity different from a staffed batch? The machine works without anyone on site, so a single unmonitored stop can burn the rest of the window. That is why the unattended uptime input usually sits well below the uptime you see during a staffed shift.
How many cycles can an overnight window hold? Multiply the hours between the last operator leaving and the first returning by the cycle rate, then derate for tool changes and planned stops. Enter the cycles you trust the machine to start unattended.
Which loss should I fix first for a lights-out run? Start with uptime. An unattended stop removes every remaining cycle in the window, while a yield loss removes only the parts from cycles that did run. Monitoring, tool-life limits, and safe park moves protect the window.
Does the target change the capacity result? No. The target good-parts figure is a plan to compare against, not part of the calculation. The gap to target row shows the difference, and the verdict warns when the window falls short.

Last reviewed 2026-10-01.