Electrical calculators
Works in your browser. Nothing is uploaded.Voltage drop and cable size
Work out the voltage lost along a cable run, and the smallest cable size that keeps it within your limit.
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A
m
V
Voltage drop
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In volts
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At the load
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Worked out with the cable at 70 °C, as it runs when loaded. For three-phase, type the voltage between two lines, such as 400 V.
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How to use it
- Describe the circuit
DC, single-phase or three-phase, copper or aluminium, and the current, length and voltage.
- Pick the cable
In mm² or AWG. The drop shows in volts and percent, with what is left at the far end.
- Compare sizes
Each size shows the drop it gives, and the smallest within your limit is ticked. Tap one to use it.
Tips
- Length one way
Type the distance from the supply to the load. The way back is counted for you.
- Three-phase
Use the voltage between two lines, such as 400 V or 480 V.
- Drop isn’t everything
A cable must also carry the current safely. Check its rating in the tables where you work.
In the app
Electrical calculator in Angle Meter
- Cable-size cards, each with its drop
- Loop impedance limits for breakers
- AC power, motors and wire sizes
- Wire colors and plugs by country
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