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Lighting Calculator

Result
—lumens
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CalcBuild › Lighting Calculator

How to Calculate Lighting

Use this free lighting calculator to get instant, accurate results for your construction project. Simply enter your measurements above and the calculator will automatically compute the result using industry-standard formulas.

Pro Tip: Always add 10-15% extra material to account for waste, cuts, and job-site conditions. This is standard practice recommended by experienced contractors.

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📊 NEC Wire Ampacity (Copper, 75°C)

AWGMax AmpsBreakerCommon Use
1415A15ALighting
1220A20AKitchen/bath outlets
1030A30ADryer, water heater
840A40ARange, large AC
655A50-60ASubpanel feeder
470A70ALarge subpanel

❓ Frequently Asked Questions

+What wire size for 20 amps?
12 AWG copper for runs under 50ft at 120V. For longer runs, upgrade to 10 AWG to minimize voltage drop.
+What is the 80% rule?
NEC says continuous loads must not exceed 80% of breaker rating. A 20A breaker carries max 16A continuously.
+Do I need a permit?
Yes for new circuits, panel upgrades, or adding subpanels. Simple switch/outlet replacements typically do not need a permit.
+Can I use aluminum wire?
Yes for large feeders (4 AWG and up). Requires anti-oxidant compound on all connections. Must be 2 sizes larger than equivalent copper.