Amps to Cable Size Calculator
Select compliant electrical wire cross-sectional sizes based on operating load currents, line voltage, and installation derating.
Amps to Cable Size Calculator
How to Use the Amps to Cable Size Converter
Selecting standard copper and aluminum cables based on design load is easy.
- 1Enter Load Current: Input circuit load in Amps.
- 2Select System Phase: Choose between Single Phase or Three Phase AC.
- 3Select Conductor Material: Select Copper or Aluminum wiring.
- 4Set Environmental Factors: Choose installation method, temperature, and cable grouping factors.
How to Calculate Amps to Cable Size (Step-by-Step Guide)
Electrical cables are sized based on their current-carrying capacity (ampacity) adjusted for thermal and installation environment factors. The formulas and mathematical workflow are presented below.
Required Ampacity Formula
Where:
- I: Circuit load design current in Amps
- Ca: Temperature derating correction factor
- Cg: Winding grouping correction factor
- Ci: Installation method thermal factor (e.g., conduit, tray, air)
Real-Life Scenario: Sizing a Conduit Feeder (40 Amps)
An electrician must size a single-phase feeder operating at 40 Amps. The wires are pulled inside a conduit conduit (Ci = 0.9) run through a ceiling space with an ambient temperature of 40°C (Ca = 0.87), bundled alongside 2 other cables (Cg = 0.70). Sizing is calculated as:
- 1Determine Correction Factors:
Ca = 0.87,Cg = 0.70,Ci = 0.90. - 2Compute Adjusted Capacity Required:
Iz = 40 ÷ (0.87 × 0.70 × 0.90) = 40 ÷ 0.5481 ≈ 72.98 Amps - 3Consult Standard IEC Cross-Section:
Locate copper standard sizes: 10 mm² handles up to 57A; 16 mm² handles up to 76A. Since 72.98A exceeds 57A, select 16 mm².
Final Output: The feeder requires a minimum of 16 mm² copper wire.
Amps to Cable Size Reference Conversion Chart
The table below displays standard IEC copper cable cross-sections and maximum current capacity under normal conditions (30°C in air, single cable):
| Current (Amps) | Cable Size (mm²) | Typical Winding Use |
|---|---|---|
| 10 A | 1.5 mm² | Lighting Circuits |
| 16 A | 2.5 mm² | Power Outlets |
| 25 A | 4.0 mm² | Water Heaters |
| 32 A | 6.0 mm² | Air Conditioning |
| 40 A | 10.0 mm² | Cooker Units |
| 63 A | 16.0 mm² | Sub-Distribution Boards |
| 80 A | 25.0 mm² | Heavy Machinery |
| 100 A | 35.0 mm² | Main Supply Feeders |
Cable Size Chart
A standard cable size chart aligns thermal current ratings with copper and aluminum cross-sections, allowing quick cross-referencing for domestic power routing.
3 Phase Cable Size Chart
A 3 phase cable size chart reflects line-to-line current ratings, taking into account balanced inductive motor loads and industrial conduit conditions.
32 Amp Cable Size
Selecting a 32 amp cable size typically yields a minimum 6.0 mm² copper conductor under conduit installation rules to prevent overheating.
Frequently Asked Questions (FAQs)
Determine the load current, apply environmental derating factors (temperature, grouping, conduit), and match the resulting adjusted capacity with standard cross-section ampacity tables.
A 6.0 mm² copper cable can handle 40 Amps if installed in free air, but is unsafe if run through thermal insulation or hot conduits where capacity drops below 34A.
A standard 2.5 mm² copper cable handles up to 20-25 Amps under typical routing conditions, supporting loads of 4.8 kW at 240V.
A 1.0 mm² copper conductor typically handles up to 10 Amps under standard conditions, suitable for low-power residential lighting loops.
Yes, a 2.5 mm² copper wire is rated for 20 Amps in most single-phase domestic ring main or socket outlet installations.
A 10 kW shower draws around 43.5 Amps at 230V. Under standard codes, a 10 mm² copper wire is required because a 6.0 mm² wire is rated below 40A in conduit.
