Wire Size Calculator
Estimate a practical wire gauge (AWG) based on amps, conductor material, and common temperature columns.
Your Wire Size Estimate
- Enter amperage — Use the expected load current in amps.
- Pick material — Copper and aluminum have different ampacity values.
- Choose a column — 60/75/90°C columns are commonly referenced in planning tables.
- Review result — The calculator returns a smallest gauge that meets or exceeds the entered amps in the selected table.
- Confirm locally — Installation conditions can change allowable ampacity. Use this as a planning estimate.
How Do I Choose Wire Size?
Wire size is commonly planned around three things: load current (amps), conductor material (copper vs aluminum), and a reference ampacity table. This calculator returns a smallest gauge that meets or exceeds your input in the selected column as a starting point.
Real installs can change what's acceptable due to temperature, bundling, insulation type, terminations, and equipment limits. Treat this as a planning estimate and verify against your local code requirements and manufacturer specs before purchase or installation.
Example: a 50A load may point you toward a mid-range gauge in copper, but a long run can still require upsizing to reduce voltage drop. If distance is part of your project, run the same scenario through the Voltage Drop Calculator to sanity-check the result.
Wire Size vs Amp‑to‑Wire Size: Which Calculator Should You Use?
These two tools are close cousins, but they answer slightly different questions. Use the one that matches the decision you are making.
Use the Wire Size Calculator when you already know circuit amps (or breaker size) and want a practical gauge recommendation with copper vs aluminum and a temperature column.
Use the Amp‑to‑Wire Size Calculator when you are starting from an appliance/load amp draw and want a fast “what gauge is this roughly?” conversion before you refine the design.
For long runs or voltage‑sensitive loads, pair either result with the Voltage Drop Calculator.
Copper vs Aluminum: Why the Gauge Changes
Copper and aluminum carry the same current differently. This quick table shows common planning pairings people compare:
| Circuit amps | Often planned (copper) | Often planned (aluminum) | Notes |
|---|---|---|---|
| 20 A | 12 AWG | 10 AWG | Aluminum typically needs a larger gauge. |
| 30 A | 10 AWG | 8 AWG | Bigger gauge helps keep heating down. |
| 50 A | 6 AWG | 4 AWG | Often compared for larger loads. |
Planning reference only. Always verify for your installation conditions and local code.
Quick Reference: Common Circuits
These are typical pairings people look up (planning reference only):
| Circuit | Typical Breaker | Often Planned Wire (Cu) |
|---|---|---|
| Lighting circuit | 15 A | 14 AWG |
| General outlets | 20 A | 12 AWG |
| Small appliance circuit | 20 A | 12 AWG |
| Dryer / range branch | 30–50 A | 10–6 AWG |
| Subpanel feeder (small) | 60–100 A | 6–3 AWG |
Your project may require a different choice depending on run length, voltage drop targets, and installation conditions.
How This Wire Size Result Is Chosen
Under the hood, this is a planning selection from common ampacity tables (you choose copper/aluminum and a temperature column).
Material effect = Aluminum typically needs a larger gauge than copper for the same amps
Next steps = If the run is long, verify voltage drop separately
This is sizing guidance for estimates and comparisons. Installation method, bundling, insulation rating, and terminations can change the required wire.
Related Calculators
Wire size depends on amperage, distance, and voltage. Browse the full electrical calculator collection.
FAQ
Is this wire size result code-compliant?
This tool is for planning estimates. Installation conditions and local code rules can change allowable ampacity. Always verify with the rules and equipment ratings that apply to your project.
Why do copper and aluminum give different wire sizes?
Aluminum has higher electrical resistance than copper — about 1.6× higher — so a larger aluminum wire is needed to carry the same current with the same voltage drop. Aluminum is cheaper and lighter, making it common for service entrance conductors and large feeder runs. For branch circuits inside homes, copper is standard. Aluminum connections require anti-oxidant compound and aluminum-rated terminals.
What wire size do I need for a 50 amp circuit?
A 50A circuit requires 6 AWG copper or 4 AWG aluminum. This is common for electric ranges, large EV chargers, and hot tubs. The circuit requires a double-pole 50A breaker. Always verify local code requirements — some applications require conduit, specific insulation ratings, or ground fault protection in addition to correct wire sizing.
What is the difference between AWG and wire gauge in mm²?
AWG (American Wire Gauge) is used in the US and Canada. European and international standards use mm² cross-sectional area. Common conversions: 14 AWG ≈ 2.5mm², 12 AWG ≈ 4mm², 10 AWG ≈ 6mm², 8 AWG ≈ 10mm², 6 AWG ≈ 16mm². When working with imported equipment or international specifications, always convert to ensure correct wire selection.
Do I need to size wire differently for continuous loads?
For planning, many people treat long‑running loads as “continuous” and keep sustained current below roughly 80% of breaker rating. Local codes differ, so treat this as a sizing sanity‑check and confirm with an electrician or your jurisdiction.