How do you convert lumens to watts?

Divide lumens by luminous efficacy in lumens per watt (lm/W): W = lm ÷ (lm/W). Example: 1,600 lm at 100 lm/W → 16 W. The efficacy depends on the light source (LED is much higher than old incandescent).

How do you convert watts to lumens?

Multiply electrical watts by efficacy: lm = W × (lm/W). Example: 10 W × 100 lm/W = 1,000 lm.

What is luminous efficacy (lm/W)?

It is how many lumens of visible light you get per watt of electrical power. Higher is more efficient. Typical ranges: incandescent ~10–17 lm/W, CFL ~50–70 lm/W, LED often ~80–120+ lm/W depending on product.

Why is there no single lumens-to-watts factor?

Lumens measure light output; watts measure electrical input. The ratio between them is not fixed—it depends on technology, design, color temperature, and driver losses.

Is a higher-lumen bulb always brighter?

Usually yes for the same beam pattern, but lumens describe total light output; perceived brightness also depends on direction, optics, and where you measure. For shopping, comparing lumens (not watts) is the right approach.

What lumens replace a 100 W incandescent?

Roughly 1,600 lm is a common “100 W equivalent” target for many markets, but always read the label. Use this converter with an efficacy you trust for your bulb type.

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Lighting Converter

Lumens to Watts Converter

Convert lumens (lm) to electrical watts (W) and watts to lumens using luminous efficacy (lm/W). Pick typical LED, CFL, or incandescent efficacies—or enter your own—to compare bulbs and estimate power.

Last updated: April 8, 2026

Bidirectional lumens ↔ watts

Adjustable lm/W (efficacy)

Quick presets for common source types

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Lumens to Watts Converter

Convert lumens (lm) to electrical watts (W) using luminous efficacy (lm/W). Choose a source type or enter a custom efficacy—LED, CFL, and incandescent differ a lot.

Quick presets (lm/W)

Luminous efficacy (lm/W)

Watts = lumens ÷ (lm/W). Must be greater than zero.

Lumens (lm)

Electrical power (W)

Summary

Lumens

1,600 lm

Watts

16 W

Efficacy used

100 lm/W

Why efficacy matters

Lumens measure light output; watts measure electrical input. The ratio (lm/W) depends on the technology—always compare bulbs using lumens and efficacy, not watts alone.

Lumens to Watts Converter Features

Core formulas

Light output vs power

Relationships

W = lm ÷ (lm/W)

lm = W × (lm/W)

Efficacy presets

Typical technologies

Examples

LED ~100–120 · CFL ~60 · Incandescent ~15 lm/W

Shopping use

Compare brightness fairly

Tip

Use lumens for brightness; use watts × efficacy to understand efficiency.

Quick Example Result

1,600 lm at 100 lm/W (typical LED):

Lumens

1,600 lm

Power

16 W

How Our Lumens to Watts Converter Works

Lumens measure total visible light output (luminous flux). Watts measure electrical power drawn by the lamp. The link between them is luminous efficacy, in lumens per watt (lm/W): how much light you get per watt. Our converter uses the standard relations W = lm ÷ (lm/W) and lm = W × (lm/W), with efficacy you choose to match your technology.