"4 machines x 24 hours" is not your real daily capacity
It is tempting to plan around the theoretical maximum: machine count times hours in a day. Real capacity is always lower, because prints fail, machines need cleaning and maintenance, and even a well-run operation does not run every machine at 100% uptime every single day. Planning against the optimistic number instead of the realistic one is a common way a small print operation ends up overcommitted to customers or deadlines it cannot actually meet.
How the plan works
Raw hours (machine count times hours per day per machine) are reduced by your stated uptime percentage, then reduced again by a maintenance buffer percentage, giving a realistic available-hours figure. The gap between the raw and adjusted numbers is shown explicitly, so you can see exactly how much capacity real-world downtime is actually costing you.
Worked example
4 machines, 20 hours/day each (80 raw hours), 85% uptime, 5% maintenance buffer: available capacity comes out to about 64.6 hours/day, roughly 15.4 hours/day lower than the raw figure, which is the gap a queue commitment based on the raw number would silently ignore.
A common mistake
A frequent error is estimating uptime from a printer's best week rather than its typical one. A machine that ran flawlessly during a quiet, closely monitored week rarely keeps that pace once it is running unattended jobs regularly. Base your uptime figure on a representative stretch of normal operation, not the best outcome you have ever seen. A month of actual logged run time versus scheduled time gives a far more honest uptime figure than an intuitive guess, and it is worth the small effort to track for a few weeks before committing to a number you will plan capacity around.
Limitations
This computes available machine-hours from the inputs you provide; it does not know your actual historical uptime or failure rate unless you measure and enter them. Revisit this estimate periodically against your real experience rather than treating it as fixed.