Lux to Lumens Converter
Lux, lumens and candela converted with the area, beam angle or distance.
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- Free preview: the rules, dates and checks that apply to your figures, with every computed amount hidden.
- Locked until you unlock it: download and copy.
- Unlock: Pro pass, ₹179 for 30 days or ₹79 for 1 week, a one-time payment that never renews. Unlock: Pro pass, $5.99 for 30 days or $2.99 for 1 week, a one-time payment that never renews.
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About the Lux to Lumens Converter
Lux and lumens measure different things: lumens are the light a source gives out, lux the light that falls on each square metre. This converter links them through the geometry that matters: an area or a room’s length and width (lux = lumens ÷ m²), a beam angle (lumens = 2π × candela × (1 − cos(angle ÷ 2))), or a distance from a point source (lux = candela ÷ distance²). It also converts luminance between nits (cd/m²) and foot-lamberts, which measure how bright a surface looks rather than how much light falls on it.
The free preview shows the result rows with the values hidden; a Pro pass shows every value, with copy and text or JSON downloads.
How to use it
- Choose what to convert: lux and lumens over an area, candela and lumens in a beam, luminance, or illuminance at a distance from a point source.
- Enter the value and choose its unit.
- Give the area (or the room’s length and width), the full beam angle or the distance, as the choice asks.
- Select Convert; with a Pro pass, copy the working or download it as text or JSON.
Formulas and units
Illuminance: 1 lux is 1 lumen per square metre, and 1 foot-candle is 1 lumen per square foot, about 10.764 lux. A beam with a full angle θ fills a solid angle of 2π(1 − cos(θ ÷ 2)) steradians, so its lumens are its candela times that. A point source of I candela lights a surface facing it at a distance d with I ÷ d² lux. Luminance: 1 nit is 1 cd/m², and 1 foot-lambert is 1/π cd/ft², about 3.426 nits (NIST SP 811, appendix B.9).
Limitations
- The beam is taken as a cone of even intensity, and the point source as lighting a surface square-on with nothing in the way. Real fittings spread light unevenly: use the maker’s photometric data for a lighting design.
- Illuminance and luminance are different quantities, and no surface reflectance is assumed to turn one into the other.
Privacy
On this device: nothing is sent
Every value is calculated on your device; nothing is uploaded or stored.
Frequently asked questions
What do I get without a pass?
Without a pass, Lux to Lumens Converter shows the rules, dates and checks that apply to your figures, with every computed amount hidden. Until you unlock it, the result can’t be downloaded or copied. A Pro, Premium or Ultimate pass, a one-time payment that never renews, unlocks the full result. The pricing page lists the passes and their prices.
How many lumens do I need for a room?
Multiply the lux level you want by the floor area: 300 lux over 20 m² needs 6,000 lumens reaching the floor. Fittings lose some of their light, so a lighting design also applies utilisation and maintenance factors.
Can I convert lux to lumens without an area?
No. Lux is lumens per square metre, so the same lumens give more lux on a smaller area. Enter the area, or the room’s length and width.