Home Electrical Engineering Cable Capacity Calculator

⚡ Cable Current Carrying Capacity Calculator

Calculate current carrying capacity, determine required cable cross-section area, analyze voltage drop, and apply derating factors for electrical conductors and cables.

Calculation Mode

Cable Parameters

Cable Configuration

Analysis Results

Select calculation mode and enter parameters to see results

Standard Cable Ratings (IEC 60364)

Current Carrying Capacity

The ampacity of a conductor depends on several factors:

I = I₀ × CF × CT × CG
Current = Base Current × Correction Factors
  • CF: Installation method correction factor
  • CT: Temperature correction factor
  • CG: Grouping/bundling correction factor

Cross Section Calculation

Cable cross-section is determined by current requirements and voltage drop:

A = (ρ × I × L) / (ΔV × 1000)
Area = (Resistivity × Current × Length) / Voltage Drop
A = I / J
Area = Current / Current Density

Voltage Drop

Voltage drop limits for different circuit types:

  • Lighting Circuits: 3% max voltage drop
  • Power Circuits: 5% max voltage drop
  • Motor Circuits: 10% starting, 5% running
  • Long Runs: May require larger conductors
ΔV = (ρ × I × L) / A
Voltage Drop = (Resistivity × Current × Length) / Area

Derating Factors

  • Temperature: Higher ambient temperatures reduce capacity
  • Grouping: Multiple cables reduce heat dissipation
  • Installation: Conduit vs. open air affects cooling
  • Soil Conditions: Thermal resistivity for buried cables
  • Load Factor: Continuous vs. intermittent loading

HOW TO USE

Enter the load current, cable length, voltage, material (copper/aluminum), and installation method. The calculator recommends the minimum safe cable cross-section size.

FORMULA USED

Voltage Drop = (2 × L × I × ρ) ÷ A
Current Density for Copper ≈ 4-6 A/mm²
Derating factors apply for bundled cables

WORKED EXAMPLE

For a 20A load at 230V over 30m using copper cable: minimum cable size ≈ 2.5 mm² to keep voltage drop below 3%.

FREQUENTLY ASKED QUESTIONS

Q: What cable size do I need for 32 amps?

A: For a 32A circuit in typical domestic wiring, 6mm² copper cable is commonly used, but always verify with local wiring regulations.

Q: Why does cable length affect sizing?

A: Longer cables have higher resistance, causing greater voltage drop. Larger cross-sections reduce resistance to maintain acceptable voltage.

Q: What is derating factor?

A: Derating reduces a cable's current capacity when cables are bundled or in high ambient temperatures to prevent overheating.

Q: Copper vs Aluminum cable — which is better?

A: Copper has higher conductivity and is preferred for smaller sizes. Aluminum is cheaper and used for large industrial cables (≥25mm²).