Convert illuminance from foot-candles to lux.
1 foot-candle = 10.764 lux (one lumen per square foot vs per square metre).
A foot candle is one lumen falling on one square foot, and a lux is one lumen falling on one square meter. Since a square meter is about 10.764 times as large as a square foot, a level of one foot candle equals 10.764 lux. To convert, multiply foot candles by 10.764, and to convert back, divide lux by the same number.
A quick estimate is to multiply by 10, so 50 foot candles is about 500 lux, while the exact answer is 538. Typical office desk levels of 30 to 50 foot candles correspond to roughly 320 to 540 lux, which matches the range recommended in many international standards.
North American drawings, standards, and light meters often use foot candles, while the rest of the world uses lux, so conversion comes up whenever designs or products cross between the two. Check the unit on a light meter before you record a reading, and keep the unit with the number in your notes to avoid confusion.
Handy conversions: 1 foot candle is 10.764 lux, 10 foot candles is 107.6 lux, 20 foot candles is 215 lux, 100 foot candles is 1,076 lux, and 500 foot candles is 5,382 lux. To convert lux back to foot candles, divide by 10.764. A quick mental estimate for lux is to multiply the foot candles by ten, with the exact answer about seven percent higher.