Electronic – My laptop USB port is outputting 5.8 V. Is this in tolerance


The USB standard is for the host to provide 5 V to peripherals. When I measure the voltage on an attached Arduino, I have 5.78 V. Is this much too high or within specification?


The measurement that gave rise to the confusion is in measuring the 5V line on the Arduino, which I understood was directly passed through from the USB port if that was the power source.

Final Update:

To end confusion, the issue was caused by a multimeter whose own battery was critically low, making the device unable to function accurately. Answers and discussion below add detail.

Best Answer

The USB specification says 4.4 V or 4.45 V to 5.25 V for VBus. Some non-standard USB supplies will be higher to combat the voltage drop over a long wire and high current, but it is not within normal specifications.

Are you measuring under load? That would be important. Most devices will regulate down and even 5 V ICs tend to tolerate up to 6 V, so it's not a great problem.