Watts to Amps Calculator

Learn how watts, volts, and amps work together. Use this simple calculator to estimate the current used by your LED lighting system.

Important: This calculator provides an estimate. Always verify electrical requirements, wire sizing, breaker sizing, and installation details with applicable codes, product specifications, and a qualified electrician.

Calculate Amps

Enter the wattage, voltage, and electrical system type.

Estimated Current
0 A

Watts, Volts & Amps Explained

Think of electricity like water flowing through a pipe:

  • Volts = electrical pressure
  • Amps = electrical flow
  • Watts = electrical power

DC Watts to Amps

For a DC system, divide watts by volts.

Amps = Watts ÷ Volts
Example:

60 watts ÷ 12 volts = 5 amps

Single-Phase AC

For AC lighting, power factor may affect current.

Amps = Watts ÷ (Volts × Power Factor)
Example:

100 W ÷ (120 V × 0.90) = 0.93 A

Three-Phase AC

For a balanced three-phase system using line-to-line voltage:

Amps = Watts ÷ (√3 × Volts × Power Factor)
Example:

10,000 W ÷ (1.732 × 208 V × 0.90) = 30.8 A

What Is Power Factor?

Power factor shows how effectively electrical power is being used in an AC system.

Power Factor = Real Power ÷ Apparent Power

For LED lighting, power factor can vary depending on the LED driver. Check the product specification sheet for the actual value.

Electrical Calculations for LED Lighting

These calculations are useful when replacing traditional lighting with LEDs or planning a new lighting installation.

When comparing LED fixtures, look at:

  • Wattage
  • Lumens
  • Voltage
  • Current
  • Power factor
  • Lumens per watt

Total LED Load

To calculate the total wattage of multiple LED fixtures:

Total Watts = Fixture Watts × Number of Fixtures
Example:

20 fixtures × 50 W = 1,000 W total

At 120 V and PF 0.90:

1,000 ÷ (120 × 0.90) = 9.26 A

Watts to Amps Quick Reference

These examples assume a power factor of 1.0.

Watts Volts Amps
10 W 120 V 0.08 A
25 W 120 V 0.21 A
50 W 120 V 0.42 A
75 W 120 V 0.63 A
100 W 120 V 0.83 A
150 W 120 V 1.25 A
200 W 120 V 1.67 A
500 W 120 V 4.17 A
1,000 W 120 V 8.33 A

Frequently Asked Questions

How do I calculate amps from watts?

For a basic DC or PF 1.0 calculation, divide watts by volts.

Amps = Watts ÷ Volts
Does LED wattage mean brightness?

No. Watts measure electrical power consumption. Lumens measure light output. When comparing LEDs, look at both wattage and lumens.

Does power factor affect LED current?

Yes. In AC systems, a lower power factor generally means more current is required for the same real power.

Can I use this calculation to select a breaker?

No. Watts-to-amps calculations are only one part of electrical design. Final wire and breaker sizing should be verified according to applicable electrical codes, equipment specifications, and qualified electrical professionals.

How do I calculate the total LED load?
Total Watts = Fixture Watts × Number of Fixtures
Upgrade to LED with confidence.
Understanding watts, volts, amps, and power factor can help you compare LED products and estimate electrical loads.