Amp to Wire Size Calculator
Find minimum wire gauge for any amperage using NEC ampacity tables, conductor material, and voltage drop.
Wire Size from Amperage
Choosing the correct wire gauge prevents overheating and excessive voltage drop. This calculator uses NEC 75°C ampacity tables for copper and aluminum conductors, with an optional voltage-drop check for long cable runs.
How Wire Size Is Selected
The minimum wire must carry the circuit current without exceeding its rated ampacity. When voltage drop is enabled, the wire must also keep drop within your limit:
$$V_{drop} = 2 \cdot I \cdot R \cdot \frac{L}{1000}$$For three-phase systems, a $\sqrt{3}$ factor applies. Related tools: 100 Amp Wire Size Calculator and 12V Wire Size Calculator.
Frequently Asked Questions
How do I pick wire size from amps?
Select a gauge whose ampacity is at least your circuit current. For long runs, also verify voltage drop stays within 3% for branch circuits or your equipment limit.
Does material matter?
Yes. Aluminum has lower ampacity than copper for the same gauge, so you often need a larger aluminum wire for the same current.
What voltage drop should I allow?
Many installations target 3% maximum drop on branch circuits. Sensitive equipment may require tighter limits.
Is this a substitute for an electrician?
No. Results are informational guides. Always follow local codes and consult a qualified electrician before installation.
Related Tools
Sensitivity Calculator
Darcy's Law Calculator
Batting Average Calculator
Markdown Formatter
Cups to Pounds Converter
Age In Weeks Calculator
T9 to Text Converter
Etsy Fee Calculator
Steak Cook Time Calculator
Mixed Number Calculator
Fishing Knot Strength Calculator
Humans Vs Vampires
Gravitational Time Dilation Calculator
Crontab Generator
Parallel Line Calculator
BUN to Creatinine Ratio Calculator
XML to C Sharp POJO Generator
Amortization Calculator
KenKen Generator (Calcudoku)
Ln Calculator