Centimeter candle:
cm*c
Flame:
fl
Foot candle :
ft*c
Lumen/square cm:
lm/cm2
Lumen/square foot:
lm*ft2
Lumen/square meter:
lm/m2
Lux:
lx
Meter candle:
mc
Nox :
nx
Phot:
ph
Watt/square centimeter:
W/cm2

Formula

L=I/S

Where,
I is the luminous intensity and S is the area of the source surface perpendicular to the given direction.