Extension Cord Voltage Drop Calculator
Long cords and heavy loads can cause voltage drop. Enter the cord length, load, voltage, and wire gauge to estimate drop.
Last updated: May 2026
Buying and sizing notes
- For high-draw tools, use a shorter and heavier-gauge cord. Check tool and cord ratings before use.
How to use this estimate
What this includes
- Cord length
- Current draw
- Voltage
- Wire gauge
- Round-trip conductor length
What it does not include
- Cord condition
- Temperature effects
- Code approval
- Motor startup behavior
Common mistakes
- Using a cord that is too long
- Assuming a thin extension cord is fine for heavy loads
- Ignoring voltage drop on motors and compressors
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