Wire Size Calculator

mm²	AWG	Copper (A)	Aluminum (A)
1.0	18	10	-
1.5	16	15	12
2.5	14	21	16
4	12	28	22
6	10	36	28
10	8	50	39
16	6	68	53
25	4	89	69
35	2	110	85
50	1	134	104

About Wire Size Calculator

The Wire Size Calculator is a professional electrical tool designed to help electricians, engineers, and DIY enthusiasts determine the correct wire gauge for any electrical installation. It calculates the appropriate wire size based on current load, voltage, distance, material type, and voltage drop constraints, ensuring safe and efficient electrical systems.

Why Wire Size Matters

Selecting the correct wire size is critical for electrical safety and system performance. Undersized wires can lead to overheating, energy loss, voltage drops, equipment damage, and fire hazards. Oversized wires, while safe, increase installation costs unnecessarily.

Proper wire sizing considers both the current-carrying capacity (ampacity) and voltage drop over distance. This calculator helps you find the optimal wire size that meets both requirements while complying with electrical codes and safety standards.

How Wire Sizing Works

Ampacity Requirement

The wire must be able to safely carry the required current without overheating. Each wire size has a maximum ampacity rating that depends on the conductor material, insulation type, and installation method.

Voltage Drop Calculation

Single Phase: VD = 2 × L × I × R / 1000

Three Phase: VD = √3 × L × I × R / 1000

Where L = length (m), I = current (A), R = resistance (Ω/km). The calculator ensures voltage drop stays within acceptable limits (typically 3% for branch circuits, 5% total).

Material Selection

Copper has better conductivity and higher ampacity than aluminum but costs more. Aluminum is lighter and more economical for large installations but requires larger wire sizes for the same current capacity.

Wire Size Standards

Wire sizes are specified using two main systems:

Metric (mm²)

Used in most countries worldwide. Specifies the cross-sectional area of the conductor in square millimeters. Common sizes: 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50 mm².

AWG (American Wire Gauge)

Used primarily in North America. Smaller numbers indicate larger wires. Common sizes: 18, 16, 14, 12, 10, 8, 6, 4, 2, 1, 1/0, 2/0, 3/0, 4/0 AWG.

Voltage Drop Guidelines

Application	Max Voltage Drop	Notes
Branch Circuits	3%	From panel to outlet
Feeder Circuits	2%	From service to panel
Total System	5%	Combined feeder + branch
Motor Circuits	3-5%	At full load
Sensitive Equipment	1-2%	Computers, medical devices

Common Applications

Residential Wiring: Lighting circuits, outlets, kitchen appliances, HVAC systems
Commercial Buildings: Office equipment, lighting, elevators, HVAC, data centers
Industrial Applications: Motors, machinery, welding equipment, heavy loads
Solar Installations: PV array wiring, inverter connections, battery banks
Automotive: Battery cables, alternator wiring, accessory circuits
Marine: Boat electrical systems, shore power connections

Typical Wire Sizes for Common Loads

Application	Current	Typical Wire (Copper)
Lighting Circuit	10A	1.5 mm² (16 AWG)
General Outlets	16A	2.5 mm² (14 AWG)
Kitchen Appliances	20A	2.5-4 mm² (14-12 AWG)
Air Conditioner	15-25A	4-6 mm² (12-10 AWG)
Electric Range	40-50A	10-16 mm² (8-6 AWG)
Main Service Panel	100-200A	35-95 mm² (2-2/0 AWG)

How to Use This Calculator

Enter the load current in Amperes
Select the system voltage (110V, 220V, 380V, etc.)
Enter the cable length (one-way distance in meters)
Choose the conductor material (Copper or Aluminum)
Select single-phase or three-phase system
Set the maximum allowable voltage drop percentage
View instant results with recommended wire size
Review voltage drop analysis and safety warnings
Check alternative wire sizes if needed
Save calculations to history or export as text file

Key Features

✓Ampacity-based wire selection
✓Voltage drop calculations
✓Copper and aluminum support
✓Single and three-phase systems
✓Metric (mm²) and AWG units
✓Power loss calculation
✓Safety warnings and recommendations
✓Alternative wire size suggestions
✓Step-by-step calculation breakdown
✓Common application presets
✓Calculation history
✓Export to text file

Safety Considerations

Always consult local electrical codes and regulations
Consider ambient temperature and installation conditions
Account for derating factors (conduit fill, bundling, temperature)
Use appropriate insulation type for the application
Ensure proper termination and connection methods
Consider future load growth when sizing wires
Hire a licensed electrician for installation
Never exceed the rated ampacity of conductors
Protect circuits with appropriately sized breakers or fuses

Frequently Asked Questions

What's the difference between wire size and wire gauge?

Wire size refers to the cross-sectional area of the conductor (mm² or kcmil), while wire gauge (AWG) is a standardized numbering system. In AWG, smaller numbers indicate larger wires (e.g., 10 AWG is larger than 14 AWG).

Should I use copper or aluminum wire?

Copper is preferred for most applications due to better conductivity, higher ampacity, and easier termination. Aluminum is more economical for large installations and long runs but requires larger sizes and special connectors to prevent oxidation.

How do I measure cable length for the calculator?

Measure the one-way distance from the power source to the load. The calculator automatically accounts for the return path in single-phase systems (factor of 2) and the phase relationship in three-phase systems (factor of √3).

What if the recommended wire size seems too large?

Large wire sizes are often required for long cable runs to minimize voltage drop. Consider reducing the distance, increasing the voltage, using three-phase power, or accepting a higher voltage drop percentage if appropriate for your application.

Does this calculator account for temperature derating?

This calculator uses standard ampacity values for typical installation conditions (30°C ambient, limited bundling). For high-temperature environments, conduit fill, or multiple cables in close proximity, apply appropriate derating factors from electrical codes.

Best Practices

Always size wires for the maximum expected load, not average load
Consider future expansion when selecting wire sizes
Use continuous-duty ratings for loads that run for extended periods
Verify wire compatibility with circuit breaker or fuse ratings
Label all circuits clearly at both ends
Use color coding to identify phases and neutral conductors
Protect wires from physical damage with appropriate conduit or cable trays
Ensure proper grounding and bonding of all electrical systems
Keep detailed records of wire sizes and circuit layouts
Perform regular inspections and maintenance of electrical installations

Disclaimer

This calculator provides estimates based on standard electrical formulas and typical installation conditions. Results should be verified by a licensed electrician and must comply with local electrical codes, regulations, and standards. The calculator is for informational purposes only and should not replace professional electrical design and installation services. Always consider specific installation conditions, ambient temperature, derating factors, and safety margins when selecting wire sizes.