3D Printing Calculators
Power Supply (PSU) Sizing Calculator
https://www.3dsizing.com/calculators/psu-sizing/
Estimate only — not firmware, a slicer profile or a shop quote. Confirm on a test print.
Power Supply (PSU) Sizing Calculator
Custom printers fail when the bed heater and hotend inrush plus motors exceed a cheap laptop brick. Sum the loads and keep 20% headroom so the supply is not sitting at 100% on every first layer.
Inputs
Results
Please tick the box above to display the Result.
Calculation method
Add bed watts, hotend watts, (motor count × watts per motor) and controller/fan watts. Recommended PSU capacity is that sum times 1.20. The 20% margin keeps the supply below full load with both heaters on: it covers heater resistance tolerance, an output trimmed above nominal voltage (heater power rises with the square of voltage), derating in a warm enclosure and ageing. PSU ratings are output watts, so conversion efficiency is not part of this margin; it only raises the power drawn from the wall. This calculator does not convert 12 V vs 24 V current — divide watts by voltage yourself for fuse sizing.
Exact formula
Running watts = bed + hotend + motors × W/motor + other. Recommended = running × 1.20. Limits: Continuous sum × 1.20, not inrush and not 12 V vs 24 V current. A wattage number is not a wiring or fuse guide.
Fuses still exist
Put a fuse or breaker on the DC output sized to the wire, not only to the PSU’s marketing watts.
Heated chambers
Enclosure heaters are extra “other watts”. They can dwarf the hotend.
Frequently asked questions
12 V or 24 V?
Same watts, half the current at 24 V, so thinner wire and less voltage drop. The wattage math here is identical.
Why only 4 W per motor?
A NEMA 17 holding is not drawing stall power while stepping. If you run high current on large motors, raise the field.
Should I size for bed + hotend both at 100%?
Yes for the first-layer worst case. PID later averages lower, but cold-start is what trips cheap supplies.
Is 20% enough?
It is a common electronics derate, not a code. Dusty enclosures and 40 °C ambient want more headroom.
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