PDU Load Calculator
Check the load on a power strip or circuit in amps and as a percentage of capacity, with the 80% continuous-load limit flagged. Calculates in your browser.
Load on circuit
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Show the math
Current is load divided by voltage; the rated capacity is voltage × the breaker amps:
amps = watts ÷ volts · safe load ≤ 80% × rating
Electrical code treats a server load as continuous, so a circuit should carry no more than 80% of its breaker rating, a 20 A circuit is good for 16 A. Balance phases and leave headroom for inrush. Calculated entirely in your browser.
What this does
A PDU load calculator checks the load on a power strip or circuit in amps and as a percentage of capacity, flagging the 80% continuous-load limit.
How to use it
- Enter the load in watts.
- Enter the voltage.
- Enter the breaker rating.
- Read amps and the 80% headroom check.
How it works
Code treats a server load as continuous, so a circuit should carry no more than 80% of its breaker rating. Headroom absorbs inrush current at power-on.
amps = watts ÷ volts
Understanding your result
The number to respect is the 80 percent continuous-load limit: code treats server loads as continuous, so a 20 A circuit should carry no more than 16 A sustained. The remaining headroom absorbs inrush at power-on and protects against tripping. Balance load across phases and circuits, and never plan to run a circuit at its full nameplate rating.
Example
A 1,920 W load on 120 V draws 16 A — the continuous limit of a 20 A circuit.
Sources & methodology
Last updated .
Frequently asked questions
How do I convert watts to amps?
Divide the load in watts by the voltage. A 1,920 W load on a 120 V circuit draws 16 A.
What is the 80% rule?
Electrical code treats a server load as continuous, so a circuit should carry no more than 80% of its breaker rating. A 20 A circuit is good for a continuous 16 A.
Why leave headroom?
Headroom absorbs inrush current at power-on and lets you balance load across phases, reducing the risk of nuisance breaker trips.
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