Wire Size & Voltage Drop Calculator

Calculate wire size and voltage drop using NEC 310.16 and IEC 60364 dual-constraint sizing engine. Snaps to commercial metric mm² and AWG with distance-to-failure simulation.

Construction Calculators

Electrical System Parameters

Dual-Constraint Sizing Engine (NEC 310.16 & IEC 60364)

Conductor Material

Maximum Allowable Voltage Drop

Circuit System

Nominal Supply Voltage

Design Load Current (Amperes (A))

One-Way Circuit Distance (Meters (m))

Equivalent:147.6 ft

Dual-Constraint Sizing Engine Results

Governed by Voltage Drop Limit (Efficiency & Code)

Thermal Ampacity MinNEC 310.16

4 mm²

10 AWG

Ampacity: 34 A (Load: 32 A)

Voltage Drop (3%) Min≤ 3%

10 mm²

8 AWG

Theoretical Area: 7.30 mm²

Final Recommended Conductor SizeVDROP DOMINANT

10 mm²

8 AWG

European Metric Standard & North American AWG Standard100% PASS

Passes Lighting / Critical Code (≤ 3%)

10 mm² (6 AWG) • 5.04 V (2.19%)

Terminal Voltage (Load)225.0 V

Real-Time Circuit Telemetry

Simulated: 10 mm² (6 AWG) • 61A (continuous at 75°C)

Voltage Drop (Vd)5.04 V

Percentage Drop (%)2.19%

Terminal Voltage (Load)225.0 V

Total Loop Resistance0.1575 Ω

Conductor Heat Dissipation161.3 W

Thermal Headroom47.5%

Distance-to-Failure Interactive Slider

Drag the slider to test longer distances. Observe when the circuit violates code thresholds.

Voltage Drop at Current Distance:2.19% (5.0V)

1 m45 Meters (m)150 m

Max Distance for 3% Drop:61.6 m

Max Distance for 5% Drop:102.7 m

Dual-Constraint Sizing Engine (NEC 310.16 & IEC 60364)

10 mm² (8 AWG) • 5.04 V (2.19%)

Commercial Conductor Sizing Matrix & Simulation

Click any row in the matrix below to simulate circuit performance with that specific cable gauge.

Commercial Size	Drop (V)	Drop (%)	Load Voltage	Heat Loss	Ampacity (75°C)	Status
1.5 mm²	33.60 V	14.61%	196.4 V	1075 W	16 A	OVERHEATING / FIRE RISK
2.5 mm²	20.16 V	8.77%	209.8 V	645 W	25 A	OVERHEATING / FIRE RISK
4 mm²	12.60 V	5.48%	217.4 V	403 W	34 A	VOLTAGE DROP FAIL
6 mm²	8.40 V	3.65%	221.6 V	269 W	44 A	VOLTAGE DROP FAIL
10 mm²REC	5.04 V	2.19%	225.0 V	161 W	61 A	RECOMMENDED
16 mm²	3.15 V	1.37%	226.8 V	101 W	82 A	PASS
25 mm²	2.02 V	0.88%	228.0 V	65 W	108 A	PASS
35 mm²	1.44 V	0.63%	228.6 V	46 W	135 A	PASS
50 mm²	1.01 V	0.44%	229.0 V	32 W	168 A	PASS
70 mm²	0.72 V	0.31%	229.3 V	23 W	213 A	PASS
95 mm²	0.53 V	0.23%	229.5 V	17 W	258 A	PASS
120 mm²	0.42 V	0.18%	229.6 V	13 W	299 A	PASS
150 mm²	0.34 V	0.15%	229.7 V	11 W	344 A	PASS
185 mm²	0.27 V	0.12%	229.7 V	9 W	392 A	PASS
240 mm²	0.21 V	0.09%	229.8 V	7 W	461 A	PASS
300 mm²	0.17 V	0.07%	229.8 V	5 W	530 A	PASS
400 mm²	0.13 V	0.05%	229.9 V	4 W	620 A	PASS

Wire Sizing & Voltage Drop Equations (NEC / IEC Standards)

DC & 1-Phase (1Φ): V_drop = 2 × L × I × ρA

3-Phase (3Φ): V_drop = √3 × L × I × ρA

Min Conductor Area: A_min = k × L × I × ρV_source × (%V_drop / 100)

Variables:

L: One-way circuit run distance in meters (factor 2 accounts for return conductor)
I: Load current in Amperes (A)
ρ: Conductor electrical resistivity at 20°C (Copper = 0.0175 Ω·mm²/m; Aluminum = 0.0282 Ω·mm²/m)
A: Conductor cross-sectional area in mm²
k: Phase coefficient (2 for DC & Single-Phase; √3 ≈ 1.732 for Three-Phase)
V_drop: Voltage drop in Volts (V) or percentage (%V_drop)

What is Wire Size & Voltage Drop Calculator?

Calculate wire size and voltage drop using NEC 310.16 and IEC 60364 dual-constraint sizing engine. Snaps to commercial metric mm² and AWG with distance-to-failure simulation. This platform eliminates the risk of electrical fires and equipment malfunction by evaluating both thermal ampacity and voltage drop simultaneously. The Dual-Constraint Sizing Engine Results panel definitively highlights which factor is dictating the wire size, ensuring your circuits remain safe under continuous load. The Real-Time Circuit Telemetry offers a live readout of terminal voltage and heat dissipation.

Practical Calculation Example

A commercial solar contractor in Arizona is wiring a heavy-duty inverter to a main breaker panel located 45 meters away. They input the 32A design load and a 230V single-phase supply. The system's dual-constraint engine determines that while a 4 mm² (12 AWG) wire can handle the heat, the distance requires a massive jump to a 10 mm² (8 AWG) conductor to keep the voltage drop under the critical 3% limit. To plan for future expansion, the contractor drags the Distance-to-Failure Interactive Slider to see exactly at what meter mark the 8 AWG wire will fail code, before hitting Copy Electrician BOM Spec to order the copper.

Conductor Ampacity & Commercial Reference Table (75°C Copper & Aluminum)

Metric Size (mm²)	North American AWG	Copper Ampacity (75°C)	Aluminum Ampacity (75°C)	Max 3% Distance @ Rated Load (230V)
1.5 mm²	14 AWG (2.08 mm²)	16 A	Not Permitted (<2.5)	18.5 m (60.7 ft)
2.5 mm²	12 AWG (3.31 mm²)	25 A	18.5 A	24.6 m (80.7 ft)
4.0 mm²	10 AWG (5.26 mm²)	34 A	25 A	28.9 m (94.8 ft)
6.0 mm²	8 AWG (8.37 mm²)	44 A	32 A	33.5 m (109.9 ft)
10.0 mm²	6 AWG (13.3 mm²)	61 A	46 A	40.3 m (132.2 ft)
16.0 mm²	4 AWG (21.2 mm²)	82 A	62 A	48.0 m (157.5 ft)
25.0 mm²	2 AWG (33.6 mm²)	108 A	83 A	56.9 m (186.7 ft)

History and Origin

The American Wire Gauge (AWG) system was created in 1857 by J.R. Brown to standardize the chaotic wire manufacturing industry. Before this, every foundry had its own proprietary sizing. By creating a logarithmic mathematical progression based on the wire drawing process, AWG allowed electrical engineers designing the early telegraph networks to accurately calculate resistance and voltage drop over vast distances.

Frequently Asked Questions

How accurate is this Wire Size & Voltage Drop Calculator tool?

Our tools utilize high-precision floating point math guaranteeing accuracy up to the 6th decimal place.

Is this free to use?

Yes, all converters and calculators on ToolsMetrics are 100% free with no limits.