| Current (A) | Min size (mm²) for ampacity | Size if length >50m (VD limited to 3%) | |-------------|-----------------------------|----------------------------------------| | 10 | 1.5 | 1.5 (short) / 2.5 (long) | | 20 | 2.5 | 4 | | 32 | 6 | 10 | | 40 | 10 | 16 | | 50 | 10 | 25 | | 63 | 16 | 35 |
Try 6 mm² Cu PVC: base rating ~47 A. Derated = 47 × 0.94 × 0.80 = 35.3 A → passes current-carrying.
| Parameter | Description | Example | |-----------|-------------|---------| | | Full load current of the circuit in amperes | 20 A | | Cable length (L) | One-way or total loop length | 50 m | | Voltage (V) | System voltage | 230 V single-phase / 400 V three-phase | | Voltage drop limit | Max allowed % drop (typically 3% for lighting, 5% for power) | 3% | | Installation method | Buried, in conduit, on tray, clipped direct, etc. | In conduit in insulated wall | | Ambient temperature | Surrounding temperature | 40°C | | Insulation type | PVC, XLPE, EPR, etc. | PVC (max 70°C conductor temp) | | Grouping factor | Number of cables bunched together | 4 circuits | | AC/DC | AC or DC system | AC 50 Hz | | Material | Copper or aluminum | Copper | cable size calculator
# Scenario: A 20 Amp load, 30 meters away, on a 230V system. # We want a max voltage drop of 3% using Copper cables. result = calculate_cable_size( current_amps=20, length_meters=30, voltage=230, allowable_v_drop_percent=3, material='copper' )
Increase to 16 mm² Cu PVC: rating ~85 A, voltage drop ~2.9 mV/A/m. ( V_d = \frac2 \times 60 \times 30 \times 2.91000 = 10.44 , V ) → 4.5% → still slightly above 3%. | Current (A) | Min size (mm²) for
# Formula Derivation: # V_drop = (2 * I * L * rho) / A # Therefore: A = (2 * I * L * rho) / V_drop # We multiply length by 2 to account for the return path (Round Trip)
If you provide your specific , I can walk you through a full manual calculation or recommend the best online tool for your region (NEC, IEC, or UK). | In conduit in insulated wall | |
A is a tool (manual formula, online app, or software) that determines the minimum cross-sectional area (e.g., mm², AWG) of an electrical cable required to safely carry a specified current under given installation conditions.