What this electrical panel occupancy calculator measures
The tool treats panel space as a physical area problem. The overall enclosure footprint is calculated from width × height. Entered device rectangles are then summed to estimate occupied device area. Reserved clearance is deducted separately because a panel can contain physically empty regions that still cannot be treated as freely available mounting space.
How the calculation works
Panel area = panel width × panel height
Device area = sum of (device width × device height)
Usable planning area = panel area − reserved clearance
Remaining planning area = usable planning area − device area
Occupancy = device area ÷ usable planning area × 100
Why clearance is separated from equipment area
A physical enclosure may contain cable entry regions, manufacturer-required clearances, barriers, ventilation zones, wiring corridors and other areas that should not be counted as free mounting space. This calculator therefore makes the reserved area explicit rather than assuming the entire enclosure footprint is available.
Worked example
For a 600 × 800 unit, the gross area is 480,000 square units. If 80,000 square units are reserved, 400,000 square units remain in the planning model. If three entered devices occupy 180,000 square units combined, estimated occupancy is 45% of the modeled usable area and 220,000 square units remain.
How to interpret the result
A lower occupancy percentage indicates more physical planning margin. A high percentage does not automatically mean an installation is unsafe or impossible; physical arrangement, manufacturer instructions, wiring space, heat dissipation, barriers and applicable rules can make some apparently empty area unavailable. Treat the result as a layout-planning aid.
Common mistakes
Do not mix millimetres with metres. Do not enter the same clearance twice. Do not assume unused enclosure floor area automatically equals usable equipment mounting area. Do not infer electrical capacity from physical space alone.
Limitations and safety
This calculation does not check equipment certification, enclosure IP/NEMA requirements, thermal performance, door swing, busbar clearance, conductor bending space, segregation, fault ratings or local electrical code requirements. Final panel layout should be checked against the actual equipment documentation and applicable requirements by a competent electrical professional.
Frequently asked questions
Does occupancy percentage tell me whether a panel complies with code?
No. It is a physical planning metric only and does not certify code compliance.
Can I enter dimensions in millimetres?
Yes. Keep every entered dimension in the same unit. The result is then expressed in the corresponding square unit.
What should reserved clearance include?
Use a planning estimate for areas you know cannot be allocated to equipment. Confirm actual clearances using manufacturer documentation and project requirements.
Can a device overlap another device in this model?
No. The calculator simply adds entered rectangular areas; it does not solve a geometric packing problem.