Cable dimensioning

Cable dimensioning: calculating the cross-section and length

The correct dimensioning of electrical cables is relevant to safety and economically important. Our calculator determines:

• Minimum cross-section: According to current carrying capacity (DIN VDE 0298-4)
• Voltage drop: Max. 3% for lighting, 5% for devices
• Maximum cable length: For a given cross-section
• Fuse protection: Suitable fuse/circuit breaker
• Type of installation: Overhead line, pipe, bundle (correction factors)

Current carrying capacity according to VDE (copper, 3 cores in conduit, 30°C):

• 1.5 mm²: 13.5 A (lighting, sockets)
• 2.5 mm²: 18 A (sockets, stove connection)
• 4 mm²: 25 A (electric stove, instantaneous water heater)
• 6 mm²: 32 A (stove, sauna)
• 10 mm²: 44 A (meter connection, distributor)

Important: Note correction factors! The load capacity decreases with increased ambient temperature, bundled cables or different installation methods. Fuse rating must be lower than load capacity: 16A fuse for 1.5mm² (13.5A load capacity) is WRONG! Correct: 13A or 10A.

Voltage drop: ΔU = 2 × I × L × 0.0178 / A (for copper). For long cables, the cross-section must be increased, even if the current carrying capacity is sufficient. Example: 50m cable, 16A, 2.5mm²: ΔU = 11.4V (5%) - borderline!