What the animation shows
The animation and the step-by-step video above use your numbers. Here is the same walkthrough written out for the default example.
What you enter
- Cord gauge: 16 AWG.
- Cord length: 50 ft.
- Tool or appliance current: 12 A.
- Outlet voltage: 120 V.
What happens, step by step
- The tool pulls 12 A out along one cord wire and back on the other.
- 16 AWG copper resists that current, so voltage sags along the cord.
- 114 V reaches the tool: 5.99 V lost, a 5% drop.
- Within 5%: fine, if the cord is rated for at least 12 A.
The answer: voltage at the tool is 114 V.
How it’s calculated
- VD = 2 × 12.9 × amps × length ÷ cmil (copper)
Worked example
16 AWG cord, 50 ft, 12 A tool at 120 V.
Inputs
- Cord gauge
- 16 AWG
- Cord length
- 50 ft
- Tool or appliance current
- 12 A
- Outlet voltage
- 120 V
Results
- Voltage drop
- 5%
- Voltage at the tool
- 114 V
- Voltage drop
- 5.99 V
Assumptions and limits
- Stranded copper cord; outlet voltage is steady under load.
Verify the result against the applicable local code, adopted code edition, manufacturer instructions and project requirements. See our methodology.
Questions
What gauge extension cord for 100 feet?
For a 12–15 A tool at 100 ft, 12 AWG keeps drop near 5%; 10 AWG keeps it lower.
Is a lower gauge number thicker?
Yes. 12 AWG is thicker than 16 AWG and carries current with less drop.