How Many Amps Does a Light Bulb Use: Complete Guide for Homeowners

Most homeowners ask how many amps does a light bulb use right after they trip a breaker or stare at a circuit panel trying to decide how many fixtures they can run on one circuit. The math is simpler than it looks, but the rules around continuous loads, NEC 210 circuit limits, and LED versus incandescent power factor catch people off guard. Here is the practical answer with the numbers you actually need.

The Watts-to-Amps Formula

Amps equal watts divided by voltage. On a US 120-volt residential circuit, a 60-watt bulb draws 60 divided by 120, or 0.5 amps. A 100-watt bulb draws 0.83 amps, and a 150-watt bulb draws 1.25 amps. That formula assumes a power factor of 1, which holds for incandescent and halogen bulbs but not for LEDs or fluorescents.

For LEDs, the power-factor coefficient typically ranges from 0.7 to 0.95. A 10-watt LED bulb draws roughly 0.09 to 0.12 amps in real-world use, slightly higher than the simple watts/volts math suggests.

Common Bulb Amp Draw at 120 Volts

• 40W incandescent: 0.33 amps
• 60W incandescent: 0.50 amps
• 75W incandescent: 0.63 amps
• 100W incandescent: 0.83 amps
• 9W LED (60W equivalent): 0.08 amps
• 13W LED (75W equivalent): 0.11 amps
• 16W LED (100W equivalent): 0.14 amps
• 26W CFL (100W equivalent): 0.24 amps
• 40W halogen MR16: 0.33 amps
• 50W halogen PAR20: 0.42 amps

Why LEDs Change the Math

LEDs use a fraction of the energy of incandescent bulbs to produce the same light output. A 9-watt Philips A19 LED matches the brightness of a 60-watt incandescent at 800 lumens. That means the same 15-amp residential lighting circuit can carry far more LED fixtures than it could with old-style bulbs.

A 15-amp circuit at 120 volts handles 1,800 watts of continuous load (1,440 watts when derated to 80 percent per NEC 210.19). That is 24 incandescent 60-watt bulbs or 160 LED 9-watt bulbs in theory. In practice you would not run anywhere near that many fixtures on one circuit, but the headroom matters when you are adding under-cabinet lights or a chandelier to an existing run.

NEC 210 Circuit Limits and the 80 Percent Rule

The National Electrical Code treats lighting as a continuous load when energized for 3 hours or more. NEC 210.19(A)(1) requires sizing the circuit to handle 125 percent of continuous load, which translates to never loading a circuit beyond 80 percent of its breaker rating. A 15-amp breaker tops out at 12 amps continuous (1,440 watts at 120V). A 20-amp circuit tops out at 16 amps continuous (1,920 watts).

Practical residential rule of thumb: count the wattage of every bulb on the circuit, add the wattage of any plugged-in fans or appliances, and confirm the total stays under 1,440 watts for a 15-amp circuit.

How Many Bulbs Per Circuit

The traditional rule was 12 fixtures per 15-amp residential lighting circuit. With LEDs, that number is wildly conservative. A modern 15-amp circuit can power 30 to 40 LED ceiling cans, 50 LED puck lights, or two large chandeliers without coming close to the load limit.

Code, not amp math, is usually the constraint. Some local codes require lighting circuits to serve no more than a certain number of rooms or square footage. Check with your local inspector before designing a large lighting layout on a single circuit.

Brand Spotlight: Real-World LED Amp Draw

Three popular LED bulbs and their actual amp draw at 120 volts:

• Philips Hue White A19 9.5W: 0.085 amps. Standard smart bulb in 800-lumen output.
• Cree TW Series 12W A19: 0.105 amps. High-CRI option for kitchens and reading nooks.
• GE Reveal HD+ 9W BR30: 0.08 amps. Recessed can replacement.

Multiply by the number of bulbs to estimate the total circuit load. Ten Hue A19s pull 0.85 amps. That is less than 6 percent of a 15-amp circuit.

What 240V and Voltage Drops Do

Outdoor low-voltage landscape lighting often runs at 12V, which increases amperage proportionally. A 10-watt 12V LED draws 0.83 amps, ten times what the same bulb would draw at 120 volts. That is why low-voltage runs need heavier-gauge wire (typically 12 or 10 AWG for long runs) to avoid voltage drop.

240V circuits (in some imported fixtures or non-US homes) cut amp draw in half compared to 120V. A 100-watt bulb on 240V draws 0.42 amps. US residential lighting almost never uses 240V, so this is mostly relevant if you are working on dual-voltage fixtures or commercial installations.

Inrush Current and LED Drivers

LED bulbs and drivers draw an inrush current at switch-on that can be 10 to 100 times the steady-state amperage for a few milliseconds. With a dozen LED cans on one switch, the inrush can trip a magnetic-only breaker, particularly with cheap drivers. Standard residential thermal-magnetic breakers handle inrush fine, but commercial DIN-rail magnetic breakers may trip on otherwise legal LED loads.

If you have nuisance tripping with LED arrays, switch to a Lutron Caseta dimmer or a Maestro LED+ in-wall dimmer. Both have inrush-tolerant outputs designed for modern LED loads.

Quick Reference: When to Add a Circuit

Add a new 15 or 20-amp lighting circuit when total bulb wattage exceeds 1,440 watts (15A) or 1,920 watts (20A) continuous, when an existing circuit nuisance-trips during evening use, or when you are renovating a room with new ceiling cans, under-cabinet lighting, and a chandelier on what used to be a single overhead light. A licensed electrician charges $250 to $700 to pull a new 14/2 or 12/2 cable from the panel to a new junction in a finished home.

Bottom Line for Homeowners

For LED bulbs, you can almost ignore amp draw on residential circuits. A typical room with 6 LED cans, 4 pendants, and a couple of lamps pulls under 1 amp total. The bigger question is which circuit serves the room and whether anything else heavy (vacuum, space heater, microwave) shares it. Track total load by listing every device on the circuit, sum the watts, and stay under the 80 percent limit. That single discipline prevents 95 percent of homeowner electrical headaches around lighting.