Lumens to Lux Calculator

About this calculator

Luminous flux in lumens (lm) measures the total quantity of visible light a source emits, while illuminance in lux (lx) measures how much of that light actually lands on a given surface: lux = lumens ÷ area in square metres. The relationship is a straightforward SI definition — 1 lux is 1 lumen spread evenly over 1 square metre — but it means the same light bulb produces very different illuminance depending on how far away and how spread out the lit surface is.

Lighting designers and architects use this conversion to check whether a fixture will meet illuminance standards for a space (office desks typically need 300–500 lux, warehouses less, surgical areas far more), and electricians and facility managers use it to verify a proposed LED replacement will provide equivalent brightness to the fixture it's replacing.