Live Demo — Cable Sizing Calculator
Enter your circuit current, voltage, run length and installation conditions to get the recommended copper cable size instantly.
Cable Sizing Calculator
Free professional cable sizing calculator for solar lighting circuits. Input the operating current, system voltage, one-way cable length, ambient temperature and allowable voltage drop to size the copper conductor by ampacity, voltage drop and short-circuit thermal stability, then round up to the nearest standard AWG cable.
Key Features
Electrical Parameters
Set the operating current (1-200 A), system voltage (12V / 24V / 48V / 220V), one-way cable length and installation method (overhead, underground, in conduit).
Environmental Parameters
Account for ambient temperature (-4 to 140°F) and whether the cable runs singly or with multiple parallel cables for correct derating.
Technical Requirements
Choose the allowable voltage drop (3% DC / 5% AC) and input the short-circuit current and duration for the thermal stability check.
Ampacity Sizing
Apply temperature and installation correction factors and require I_cable ≥ I_work × K_temp × K_install for safe current carrying capacity.
Voltage Drop Sizing
Compute ΔU = (I × ρ × L) / S with copper resistivity 0.0175 Ω·mm²/m and derive the conductor section that keeps the drop within limits.
Thermal Stability
Verify the minimum cross-section S_min = (I_short × √t) / C, then recommend the largest AWG size with the actual voltage drop shown.
Technical Specifications
| Platform | HTML5 Web App | Android (via WebView) |
| Core Calculation | ΔU = (I × ρ × L) / S; I_cable ≥ I_work × K_temp × K_install; S_min = (I_short × √t) / C |
| Operating Voltage | 12V / 24V / 48V / 220V |
| Operating Current | 1 - 200 A |
| Cable Length | 3 - 1,640 ft (one-way, doubled in calculation) |
| Allowable Drop | DC ≤ 3% / AC ≤ 5% |
| Short-Circuit | 100 - 10,000 A for 0.1 - 5 s |
| Conductor | Copper, ρ = 0.0175 Ω·mm²/m; #12 - #1/0 AWG |
| Industry Standards | IEC 60364-5-52, AS/NZS 3008.1, BS 7671, NEC 690 |
| Output | Recommended AWG cable size + actual voltage drop (V and %) |
Frequently Asked Questions
Why does the calculator use twice the entered cable length?
Voltage drop occurs on both the outbound and return conductors of a DC circuit, so the one-way length you enter is automatically multiplied by 2 before the voltage-drop calculation is performed.
What does the temperature correction factor do?
Higher ambient temperatures reduce a cable's current-carrying capacity. The factor derates the required ampacity (I_cable ≥ I_work × K_temp × K_install) so the conductor never exceeds its rated operating temperature even on hot days.
Why is the drop limit 3% for DC and 5% for AC?
12V / 24V DC solar lighting circuits are very sensitive to voltage loss because a small voltage drop is a large percentage of the bus voltage, so a tighter 3% limit protects lamp brightness and battery charging. AC circuits at 220V tolerate a 5% drop.
What does the recommended result combine?
The calculator takes the largest cross-section required by the ampacity, voltage-drop and thermal-stability checks and rounds it up to the nearest standard AWG size. It then reports the actual voltage drop of that cable so you can confirm the selection is safe and within limits.
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