Convert lux readings to PPFD (µmol/m²/s) for grow light planning, or convert PPFD to lux. The conversion factor depends on the light source spectrum — select yours below for the most accurate result.
Please enter a value to convert.
Affiliate link – we may earn a small commission at no cost to you
A lux meter measures light as the human eye sees it, with the most weight on green and yellow light. Plants use light differently, mostly in the range from 400 to 700 nanometers, and they respond to the number of photons, not to how bright the light looks to us. PPFD, in micromoles per square meter per second, measures the photons plants can use, so it is the better measure for grow lights.
Converting between lux and PPFD depends on the spectrum of the light source, because the same lux value contains different numbers of photons for different light colors. Sunlight is roughly 54 lux per unit of PPFD, high pressure sodium lamps are higher, and white LEDs are somewhere in between, while light with a lot of red and blue gives far fewer lux for the same PPFD.
The converted numbers are estimates. For serious growing, a quantum sensor that measures PPFD directly is far more accurate than a lux meter with a conversion. Use the results to compare setups and decide how far to hang a light, and watch the plants, since different species and growth stages need different light levels.