U.S. Electrical and HVAC Calculators
Free calculators for voltage drop, wire size by voltage drop, and window air-conditioner sizing. Made for electricians, apprentices, HVAC technicians, and careful DIY work in the United States.
Results are estimates only. They are not a substitute for the electrical or mechanical code, manufacturer instructions, or design by a licensed electrician or HVAC contractor.
Voltage drop calculator
Find how many volts you will lose on a run, and whether you stay within a 3% or 5% target. The calculator uses a DC-resistance method and published U.S. government wire data.
Open the voltage drop calculatorWire size calculator
Get a suggested AWG size that meets your voltage-drop limit. This is not an ampacity calculation. You still have to check the chosen size against the local codebook for current-carrying capacity.
Open the wire size calculatorBTU / air conditioner sizing calculator
Estimate the cooling capacity, in BTU/h, for a room window air conditioner, using the EPA ENERGY STAR method.
Open the BTU calculator