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.

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Units

Results

Estimated running load: 295W
PSU size with 20% margin: 354W

Recommended gear

Mean Well 24 V PSU
A named industrial supply with real ratings beats an unbranded “360 W” brick that sags at 200 W.
Typical range: $35–$90
NEMA 17 steppers
Motor count drives a smaller share of watts than the bed, but each extra axis is still a few watts continuous.
Typical range: $10–$25

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 covers efficiency, aging and the fact that a bed heater’s peak is higher than its PID average. 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. This is a continuous-load estimate, not an inrush or 24 V vs 12 V wiring guide. 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.

Disclaimer — no professional advice, no liability

Mains wiring, fusing and PSU earthing are electrical work. A wattage number is not permission to undersize wire or skip a fuse. Mean Well (and clones) must be mounted with airflow.

These calculators, pages and any related content are provided “as is” and “as available”, solely for general educational and informational purposes. They are simplified mathematical estimates, not firmware, slicer profiles or a production quote, and they do not constitute engineering, electrical, chemical or other professional advice.

Results can be wrong, incomplete or inapplicable to your printer, hotend, resin, material, firmware or use case. You must independently verify every figure, assume all risk, and confirm settings on a test print before a job that can damage a machine, start a fire or injure someone.

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Power Supply (PSU) Sizing Calculator

Inputs

Results

Recommended gear

Calculation method

Exact formula

Fuses still exist

Heated chambers

Frequently asked questions

More in this topic

Bed Heater Power Requirement

Nozzle Size vs Layer Limits

Stepper Motor Torque Requirement Estimator