Measure before you size
Replace the guess with a real watt.
A charger label is a ceiling, a compressor cycles and a motor starts differently from how it runs. Choose the measurement path that matches the circuit, then use the result in the calculators.
Choose a measurement path →Measurement path
What are you measuring?
Do not bridge circuit types with a travel adapter or improvised cable. Start with the electrical path itself.
ET920 USB Digital Meter
Checking phone, tablet and compatible USB-C charging energy without opening a mains circuit.
3–20V DC · up to 3A USB-A / 5A USB-CAlready have a measurement?Use average watts for runtime and observed peak for output.
Open Runtime Lab →A calmer measurement method
One load. One complete cycle. One honest margin.
- 01Use a meter designed for the exact AC, USB or DC path.
- 02Measure long enough to include cycling, standby and normal use.
- 03Keep average watts, total Wh and the highest observed start separate.
- 04Enter the result in Runtime Lab, then leave a reserve for uncertainty.