Calculating UPS

Use this free calculating ups to estimate UPS battery backup runtime and the VA rating you need.

How the calculating ups works

Runtime = battery volts × amp-hours × efficiency ÷ load watts. Suggested VA = load ÷ 0.7 power factor + 25% headroom.

Frequently asked questions

Which UPS size should I buy?

Pick a UPS rated above the suggested VA and check the runtime at your real load.

Results are estimates for general information only. They are not a substitute for professional advice where applicable. Found a mistake? Report an error.