Watts to Lumens Converter Formula

Understand the math behind the watts to lumens converter. Each variable explained with a worked example.

Use the Watts to Lumens Converter

Formulas Used

Estimated Lumens

lumens = watts * efficacy

Incandescent Equivalent

incandescent_equiv = watts * efficacy / 14

Variables

VariableDescriptionDefault
wattsBulb Wattage(W)10
efficacyBulb Type (Efficacy)(lm/W)90

How It Works

Watts to Lumens

Lumens = Watts x Luminous Efficacy (lm/W)

Typical Efficacy by Bulb Type

| Bulb Type | Efficacy (lm/W) | |---|---| | Incandescent | 12-17 | | Halogen | 16-24 | | CFL | 50-70 | | LED | 80-120 | | High-efficiency LED | 100-150 |

A 10W LED produces roughly the same light as a 60W incandescent bulb.

Worked Example

10 watt LED bulb.

watts = 10efficacy = 90
  1. 01Lumens = 10W x 90 lm/W = 900 lumens
  2. 02Incandescent equivalent = 900 / 14 = 64W

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