A 100 foot 16-2 gauge cord with a 120 volt source, and a load of 3.3 amps would have a voltage drop of:
Voltage drop: 2.65
Voltage drop percentage: 2.21%
Voltage at the end: 117.35
16-2 gauge cord max amps: 10.
A 100 foot 14-2 gauge cord with a 120 volt source and a load of 3.3 amps would have a voltage drop of:
Voltage drop: 1.67
Voltage drop percentage: 1.39%
Voltage at the end: 118.33
14-2 gauge cord max amps: 15
Here is the link to the voltage drop calculator:
http://www.calculator.net/voltage-d...=150&distanceunit=feet&eres=3.3&x=109&y=21
NEC requires a maximum voltage drop on a circuit of 5% and a max voltage drop on a branch circuit of 3%. Your extension cord is considered a branch circuit. These calculations are based on a 120V source feeding your extension cord, if the source voltage is less than your voltage drop will increase.
Next, if you are using an extension cord outdoors make sure it is listed, Sunlight Resistant and Wet location use and please make sure it’s source is connected to a GFCI receptacle.