Note 1 to entry: 1 lx is equal to the illuminance produced on a surface of area 1 m² by a luminous flux of 1 lm uniformly distributed over that surface.

Note 2 to entry: Non-metric, non-SI units: lumen per square foot (symbol: lm·ft⁻²), footcandle (symbol: fc):

1 lm·ft⁻² = 1 fc = 10,764 lx.

Note 3 to entry: This entry was numbered 845-01-52 in IEC 60050-845:1987.