Cable Size & Voltage Drop Calculator
Use this kabel calculator to estimate the recommended cable cross-sectional area (mm²) based on current, length, material, and allowable voltage drop.
What Is a Kabel Calculator?
A kabel calculator helps you estimate the correct cable size for an electrical circuit. The right cable size matters because it affects voltage drop, heat buildup, efficiency, and overall safety. If a cable is too small, you can get poor equipment performance and higher risk of overheating.
This calculator is designed as a practical planning tool for homeowners, students, and technicians. It combines two key checks:
- Voltage drop sizing (performance-focused)
- Current density sizing (basic thermal sanity check)
How to Use the Calculator
1) Choose the system type
Select DC, single-phase AC, or three-phase AC. This changes the electrical model used for voltage drop calculations.
2) Enter known electrical values
You can enter either current directly, or power and let the tool estimate current. For AC systems, power factor is used in the current calculation.
3) Add cable length and allowed drop
Use one-way cable length in meters. Typical design limits are around 3% for branch circuits, but local standards may vary.
4) Run calculation and review output
The calculator returns a recommended standard cable size, expected voltage drop, and estimated resistive power loss.
Formulas Used
Voltage-drop area requirement:
- DC / Single-phase: A = (2 × I × ρ × L) / Vdrop
- Three-phase: A = (√3 × I × ρ × L) / Vdrop
Where A is conductor area (mm²), I is current (A), ρ is resistivity (Ω·mm²/m), L is one-way length (m), and Vdrop is allowed voltage drop in volts.
Copper vs Aluminum
Copper has lower resistivity and generally allows smaller cross-sectional area for the same voltage drop. Aluminum is lighter and often cheaper, but usually needs larger sizing to deliver equivalent electrical performance.
- Copper resistivity used: 0.0175 Ω·mm²/m
- Aluminum resistivity used: 0.0282 Ω·mm²/m
Example Scenario
Suppose you run a 230V single-phase load at 20A over a 30m one-way cable, with a 3% maximum drop. The calculator will compute the required area from voltage drop, compare it with thermal density guidance, and then select the next standard size (for example 6 mm² or 10 mm² depending on material and limits).
Important Notes
- This is a planning calculator, not a replacement for electrical code compliance.
- Installation method, insulation rating, ambient temperature, grouping, and protection devices also affect final cable size.
- Always verify with local standards and a qualified electrician before final installation.