Electricity is one of the greatest marvels on earth. Ever since it has been discovered, man has done all that he could to harness it. Being able to conduct fundamental electricity calculations is a skill you must have in order to be successful in any project requiring electrical work. One of the properties of electricity is its amperage. If your project will require you to run electrical lines over a distance, you will need to be able to calculate the amperage drop over a distance.
Multiply the current you will be sending through your line by the total round-trip distance that you will be sending it.
Take the number that you got by multiplying these two factors and double it. This is the same as multiplying it by a factor of two. Save this number.
Determine the ohms of resistance for every one thousand feet of line that you are sending the electricity through. You can attain this information from the person you bought your electrical line from. Multiply resistance ohms by the number that you have attained from the previous calculation.
Multiply this number by the wattage you are sending through the line. This yields amperage drop over a distance.