Cable Rating Calculator

Calculate the true current-carrying capacity of any cable using the IEC 60364-5-52 formula Iz = Itab × k1 × k2 × k3 × …, where Itab is the tabulated base rating and k1, k2, k3 are the ambient temperature, grouping, and soil thermal resistivity correction factors. Multiple factors multiply together, so the combined derating can be substantial and must never be ignored.

Apply ambient air correction per IEC Table B.52.14 (reference 30°C) and ground temperature correction per Table B.52.15 (reference 20°C). The factor depends on insulation: at 40°C ambient, PVC (70°C max) drops to 0.87 while XLPE (90°C max) stays at 0.91. NEC users get Table 310.15(B)(1) factors, where 41–45°C gives 0.82 and 46–50°C gives 0.75 for 75°C-rated conductors.

Account for mutual heating when circuits share a route using Tables B.52.17–B.52.20 (bunched, single layer on wall/floor, on tray, or buried). Soil thermal resistivity correction per Table B.52.16 uses the 2.5 K·m/W reference — in moist soil (1.0 K·m/W or below) the rating can increase by up to 28%, while dry or sandy soil significantly reduces it. NEC conduit-fill adjustment per Table 310.15(C)(1) gives 0.80 for 4–6 conductors and 0.70 for 7–9.

Verify voltage drop against IEC 60364 limits of 3% for lighting and 5% for other circuits. Three-phase: ΔU = √3 × I × L × (R·cosφ + X·sinφ). Single-phase: ΔU = 2 × I × L × (R·cosφ + X·sinφ). The app selects the smallest standard cable size whose derated Iz exceeds the design current and whose voltage drop stays within the limit — the voltage drop check often governs on runs over roughly 50 m.

Switch between IEC 60364-5-52, BS 7671, and NEC/NFPA 70:2023 methodologies in one app. Each standard uses its own installation methods, reference conditions, derating tables, and voltage drop limits. The app applies the correct tables automatically, including the NEC 110.14(C) termination temperature check that is the single most common source of NEC sizing errors.

Generate professional PDF reports documenting design current, protective device rating, installation method, every applied correction factor, derated Iz, voltage drop percentage, and selected cable size with clause references. Export to CSV for integration into electrical design packages. Fully functional offline — no data leaves the device.