Does my data get uploaded anywhere?
No. Everything runs locally in your browser and nothing is sent to a server.
Is this free to use?
Yes. It is completely free, with no account, no signup, and no usage limits.
Does it work on a phone?
Yes. The page runs in any modern mobile browser, on iPhone and Android alike, with no app to install.
How many lux is one foot-candle?
10.763910416709722 lux. The factor is exact, and it is the same 10.7639 that converts square feet to square meters, because both units are lumens per unit area and only the area unit changes.
Can I convert lumens to lux?
Not directly, because lumens measure total light output and lux measures light per square meter. Lux equals lumens divided by the illuminated area, so an 800 lumen bulb spread evenly over 4 square meters gives 200 lux. This converter has no area field, so do that divide yourself.
How many lux do I need for reading or office work?
Common guidance is 300 to 500 lux for reading and general office tasks, which is 28 to 46 foot-candles. Detailed work such as drafting or fine assembly is often specified at 750 to 1,000 lux, and corridors at around 100 lux.
Is a nit the same as a lux?
No. A nit is a candela per square meter, which measures luminance, the light coming off a surface toward you, and is how screen brightness is specified. Lux measures illuminance, the light falling onto a surface. A 1,000 nit phone screen and a 1,000 lux room are unrelated quantities.
Why does the lux to foot-candle factor match the square meter to square foot factor?
Because both illuminance units are lumens divided by an area. Change the area unit from square meters to square feet and the number changes by exactly the same factor that separates the two areas, 10.7639104167.