How to calculate the combined current of all USB peripherals

I recently purchased a (non-powered) USB 3.0 data hub with four ports. When I had a cursory glance at the documentation that came with it, I saw it says connected devices should not exceed a combined current of 900mA. I have connected: Keyboard USB-C cable (usually with Android device connected) USB flash drive DAW The DAW has a current of 0.5A. The other items don't state it explicitly. According to the guide in the hub instructions, it suggests a keyboard is usually rated at 500mA. That seems quite high, but if correct would put the combined current over the total. Is there a way I can calcu

Question by alstr on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.