Engineering CalculationCable Size Calculator - Current, Derating, Voltage Drop & Short-circuit (IEC 60364)
Size a new LT cable or check an existing one in one guided flow: load current, installation method, derating for temperature and grouping, voltage drop and short-circuit withstand.
Open the calculator →Formula
Ib ≤ In ≤ Iz (design current ≤ protective device rating ≤ derated cable capacity)
Iz = Itable × Ct (temperature) × Cg (grouping)
Short-circuit withstand: S ≥ (I × √t) / k
Worked example
Fault current 10 kA cleared in 0.1 s, PVC-insulated copper (k = 115)
S = 10000 × √0.1 / 115 = 27.5 mm² → choose the next standard size, 35 mm²
Where engineers use it
- Motor and feeder cables in industrial plants
- Checking whether an existing cable can take extra load
- Preparing cable schedules
How to use
- Click Open the calculator. It runs free in your browser, on desktop or phone.
- Enter your values. Units and typical ranges are shown next to each input.
- Read the result and the step-by-step working, then print or add it to your Project BOQ.
Questions
Which standard does it follow?
The sizing logic follows IEC 60364-5-52 current-carrying capacity and derating method. Always cross-check with the cable maker's catalogue.
Does it handle aluminium cables?
Yes, copper and aluminium conductors are both supported.