Current describes the flow rate of electrons/holes at a particular point in a circuit. The SI unit of measurement for current is an Amp (A). Portable devices often operate in the low ranges of microamps (μA) or milliamps (mA).

You can use current measurements to help calculate a variety of power and energy estimations, such as how long a battery can power a device, or how much energy a device uses in a day.

Current measurements must be performed on a live circuit. If done improperly, you can damage the circuit and your multimeter, and risk electric shock. Take note of these precautions when you measure current:

Your multimeter acts like a short-circuit when it's in current measurement mode. Be very aware of what you touch with the multimeter probes to prevent unintentional short circuits, which can damage your circuit or the multimeter.

Power down the circuit while you set up. You can easily short something with your probes if you set up on a live circuit. This can damage your circuit and your multimeter.

Many multimeters will have a low and high current port, as they're protected by different fuses. The current limits are normally printed next to the port. If the current exceeds the limit for a short period of time, it will blow the associated fuse. If this happens to your iFixit multimeter, follow this guide to replace the fuse.