Lux to Lumens Calculator

Lux measures how much light hits a surface, but lumens measure the total light output of a source — the Lux to Lumens Calculator converts between the two. Enter your illuminance in lux, select your area unit, choose between a flat surface or spherical light source, and enter the surface area (or sphere radius) to get the luminous flux in lumens. Secondary outputs include the conversion factor and calculated area in m².

lx

The amount of light falling on a surface

Total area to be illuminated

Radius for spherical light source calculation

Results

Luminous Flux

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Conversion Factor

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Calculated Area

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Frequently Asked Questions

What is the difference between lux and lumens?

Lux measures illuminance (light intensity on a surface), while lumens measure luminous flux (total light output from a source). Lux = lumens per square meter.

How do I convert lux to lumens?

Multiply lux by the surface area in square meters: Lumens = Lux × Area (m²). For square feet, use the conversion factor 0.09290304.

When should I use the spherical light source calculation?

Use spherical calculation for point light sources like bulbs where light radiates in all directions. The formula uses 4πr² as the surface area of the sphere.

What are typical lux levels for different applications?

Office work requires 300-500 lux, reading needs 500-750 lux, detailed tasks require 750-1000+ lux, and outdoor daylight ranges from 10,000-100,000 lux.

Why do I need to specify the surface area?

Lumens represent total light output while lux measures light per unit area. To convert between them, you must know the area over which the light is distributed.

Can I use this calculator for LED lighting design?

Yes, this calculator helps determine the total lumens needed from LED fixtures to achieve desired lux levels on work surfaces or in rooms.

What's the conversion factor for square feet to square meters?

One square foot equals 0.09290304 square meters. This factor is automatically applied when you select square feet as your area unit.