AC Cable Size Calculator

Plan safe, efficient wiring for residential, commercial, and industrial systems easily. Enter load, voltage, power factor, length, and installation method for analysis quickly. Calculator estimates current, voltage drop, and selects nearest standard cable size automatically. Review results, export CSV, or download detailed PDF report.

Cable sizing input

Example data table

Typical scenarios for reference only; always verify against local standards.

Scenario System Load Voltage (V) Length (m) Material Drop (%) Recommended (mm²)
Small air conditioner Single 2.5 kW 230 15 Copper 3 2.5
Apartment distribution Three 12 kW 400 40 Copper 3 16
Warehouse feeder Three 45 kW 400 80 Aluminium 4 70

Formula used

1. Load current from power

Load entered as kW, kVA, or HP is first converted to equivalent active power in kilowatts.

Single-phase: I = P × 1000 / (V × PF × η)

Three-phase: I = P × 1000 / (√3 × V × PF × η)

2. Design current with safety margin

Idesign = I × (1 + m/100), where m is the chosen safety margin in percent.

3. Minimum cross-sectional area by current

AI = Idesign / (J × Ctemp × Cgroup), where J is base current density and C terms are correction factors.

4. Minimum cross-sectional area by voltage drop

Single-phase: AVD = 2 × Idesign × ρ × L / ΔV
Three-phase: AVD = √3 × Idesign × ρ × L / ΔV

where ρ is conductor resistivity (ohm·mm²/m), L is one-way length (m), and ΔV is the allowed voltage drop (V).

5. Design area and standard size

Areq = max(AI, AVD).
The calculator then selects the next higher standard cable size (mm²).

How to use this calculator

  1. Select system type as single-phase or three-phase.
  2. Choose whether to enter load power or load current.
  3. If using power, pick kW, kVA, or HP as unit.
  4. Provide voltage, cable length, and acceptable voltage drop percentage.
  5. Set safety margin, ambient temperature, and number of loaded circuits.
  6. Select conductor material and typical installation method.
  7. Press “Calculate cable size” to get recommended cross section.

Results are based on simplified assumptions and typical current densities. Always confirm final sizing using manufacturer data and applicable wiring regulations.

Key design notes

Typical voltage drop limits

Many low-voltage distribution systems adopt three to five percent total drop from source to farthest outlet. This tool lets you choose a project-specific limit.

Copper versus aluminium conductors

Copper offers better conductivity and smaller cross section, but is heavier and more expensive. Aluminium is lighter and cheaper yet usually requires larger sizes for similar performance.

Influence of temperature and grouping

Higher ambient temperature and multiple loaded circuits reduce current-carrying capacity. The calculator applies simplified correction factors to increase the selected cross-sectional area.

Compliance with wiring standards

National and local wiring rules may specify different current ratings, correction factors, and voltage drop limits. Always compare calculator output with the latest applicable standards.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.