Calculate cable cross section

📏 Cable Cross-Section Calculations

The correct cable cross-section is crucial for safety and efficiency. Our calculators help you determine the optimal cross-section based on current, length, and voltage drop.

Available Calculations:

DC: A = (2 × I × L) / (K × Δu × U)

Cable cross-section for direct current

AC: A = (2 × I × L × cosφ) / (K × Δu × U)

Cable cross-section for alternating current

Three-Phase: A = (√3 × I × L × cosφ) / (K × Δu × U)

Cable cross-section for three-phase current

Significance of Cable Cross-Section

An undersized cable can lead to overheating and voltage drops, while an oversized cable is unnecessarily expensive. The calculation considers current, cable length, conductivity, and permissible voltage drop.

DC Cable Cross-Section
A = (2 × I × L) / (K × Δu × U)

Calculate the cable cross-section, maximum current, maximum cable length, or voltage drop.

A = (2 × I × L) / (K × Δu × U)

💡 Enter the known values – leave the field you want to calculate empty.

✅ Result:

Example Calculation:
A 24 Volt DC motor has a rated current of 2.47 Ampere, a cable length of 28 m, and the voltage drop of the cable is 2%. What cable cross-section results from these values?
A = (2 × I × L) / (K × Δu × U)
A = (2 × 2.47 A × 28 m) / (56 × 0.02 × 24 V)
A = 138.32 / 26.88
A = 5.15 mm²

The next larger suitable cross-section is 6 mm²!

Units of Measurement:
Cross-section A = mm²
Voltage U = Volt [V]
Current I = Ampere [A]
Kappa Copper K = 56 [m / Ω × mm²]
Delta U Δu = %

AC Cable Cross-Section
A = (2 × I × L × cosφ) / (K × Δu × U)

Calculate the cable cross-section, maximum current, maximum cable length, or voltage drop.

A = (2 × I × L × cosφ) / (K × Δu × U)

💡 Enter the known values – leave the field you want to calculate empty.

✅ Result:

Example Calculation:
A 230 Volt AC standard motor has a rated current of 25.18 Ampere, a cos φ of 0.86, a cable length of 72 m, and the voltage drop of the cable is 2%. What cable cross-section results from these values?
A = (2 × I × L × cosφ) / (K × Δu × U)
A = (2 × 25.18 A × 72 m × 0.86) / (56 × 2% × 230 V)
A = 3118.29 / 257.60
A = 12.105 mm²

The next larger suitable cross-section is 16 mm²!

Units of Measurement:
Cross-section A = mm²
Voltage U = Volt [V]
Current I = Ampere [A]
Kappa Copper K = 56 [m / Ω × mm²]
Delta U Δu = %
cos φ = unitless

Three-Phase Cable Cross-Section
A = (√3 × I × L × cosφ) / (K × Δu × U)

Calculate the cable cross-section, maximum current, maximum cable length, or voltage drop.

A = (√3 × I × L × cosφ) / (K × Δu × U)

💡 Enter the known values – leave the field you want to calculate empty.

✅ Result:

Example Calculation:
A 400 Volt three-phase asynchronous motor has a rated current of 25 Ampere, a cos φ of 0.89, a cable length of 94 m, and the voltage drop of the cable is 2%. What cable cross-section results from these values?
A = (√3 × I × L × cosφ) / (K × Δu × U)
A = (√3 × 25 A × 94 m × 0.89) / (56 × 2% × 400 V)
A = 3622.48 / 448
A = 8.09 mm²

The next larger suitable cross-section is 10 mm²!

Units of Measurement:
Cross-section A = mm²
Voltage U = Volt [V]
Current I = Ampere [A]
Kappa Copper K = 56 [m / Ω × mm²]
Delta U Δu = %
cos φ = unitless
√3 or 1.732 = unitless

Cable cross-section formulas

The calculator determines the cross section of copper connecting cables, for example for electric motors. Depending on the network:

  • Direct current: A = (2 × I × L) / (K × Δu × U)
  • Alternating current (single phase): A = (2 × I × L × cos φ) / (K × Δu × U)
  • Three-phase current: A = (√3 × I × L × cos φ) / (K × Δu × U)

A is the cross section in mm², I is the current in amperes, L is the cable length in meters, U is the voltage in volts, Δu is the permissible voltage drop as a decimal number (2% = 0.02) and K is the conductivity of copper with 56 m/(Ω × mm²). Conversely, the maximum current, the maximum cable length or the voltage drop can also be calculated.

Calculation example alternating current

A 230V AC motor has a rated current of 25.18A and a cos φ of 0.86. The cable length is 72 m, the voltage drop may be 2%.

A = (2 × 25.18A × 72m × 0.86) / (56 × 0.02 × 230V)
A = 3118.29 / 257.60
A = 12.1mm²

The next larger standard cross-section is chosen: 16mm².

Important note

The conductor cross section should not only be selected based on the current carrying capacity. Protection against dangerous body currents, overload and short-circuit currents as well as voltage drops must also be taken into account. Cables that are operated above the permissible temperature for a long time can become damaged and fail prematurely. The calculators are only used to roughly determine the cable cross section.