title_body: How to determine the lowest safe ESC current rating for a drone build? I was planning to build a quadcopter and was wondering how I should decide what ESC to get. I'm asking about ESC current ratings. I am building a 7 inch drone using 4s with 2306 1900Kv motors. I have seen ESCs ranging anywhere from 25 amp to 50 amp frequently used on 4s quadcopters. I am looking to get the lowest amp ESC that will work for my drone because of cost.  Are there ways to figure out the minimum ESC amp-rating that will work safely for my drone?
upvoted_answer: I think most people just copy other builds, and step up a size if they burn out any ESCs.
  
  If you want to be more scientific you could test one motor with a watt-meter to measure the current draw. Throttle up slowly so you can watch the current build, to protect the ESC you're using for the test. Also check the motor temperature after 30 seconds or so.
  
  This will give you the maximum current that each ESC needs to handle.
  
  There are lots of different designs of watt-meters available for hobby use. They typically measure up to 100amps so should all be adequate for this test, and cost less than a set of ESCs.
  
  A typical multi-meter will only measure up to 10amps and would not be adequate. Clamp meters typically only measure AC current, and we need to measure the DC current from the battery to the ESC. 
  
  Fix the motor to something solid, like a plank of wood that is clamped to a bench. Be careful that the wires and other loose material will not be sucked into the prop, and don't stand in-line with the prop, just in case breaks and throws the blades out at high speed. Even a couple of hundred watts is quite intimidating in a bench test. 
  
  Alternately, you could search the forums to see if anyone else has tested a similar motor with a similar voltage battery and prop.