Calculate the cross-section of copper or aluminum cable based on power, length, and allowable voltage drop.
The cable cross-section calculator determines how thick a cable you need for your load when the cable length and allowable voltage drop are known. A cable that is too thin will overheat and the voltage will drop too much, causing the device to function poorly.
The calculator is free, works in your browser without registration, and shows the result as soon as you change the values. The calculation is done on your own device and the information you enter is not sent anywhere.
Current I = P / U (single-phase) or P / (√3 × U) (three-phase). Cross-section S = 2 × ρ × L × I / ΔU (single-phase) or √3 × ρ × L × I / ΔU (three-phase), where ρ is the resistivity of the conductor (copper 0.0175 Ω·mm²/m, aluminum 0.028 Ω·mm²/m).
A 3,000-watt device located 30 meters away on a 230-volt network with a 3 percent voltage drop requires at least about 2.5 mm² of copper cable, and the standard size is 2.5 mm². With default settings, the calculator gives a result of: Minimum cross-section 1.98 mm².
For electrical engineering students, renovators, and designers who want to estimate cable size. Actual installations should be performed by a qualified electrician.
The resistance of the cable causes a voltage decrease under load. Generally, a voltage drop is considered acceptable if it is below 3–5%.
No. The cable must also withstand the load current (current-carrying capacity) and the fuse must protect the conductor.
Permanent electrical installations must be carried out by a professional electrician according to the law. The calculator is intended as a design aid.