Photometric Units SI Units Quantity Unit Luminous flux lumen lm Luminous intensity candela cd Luminance cd/m2 Illuminance lm/m2 lx Non-SI Units Luminous Intensity candlepower = the candela Luminance 1 stilb = 1 cd/cm2 = 10,000 cd/m2 1 apostilb = (1/p) cd/m2 = 0.3183 cd/m2 1 lambert = (10,000/p) cd/m2 = 3183 cd/m2 1 millilambert = 0.001 lambert = 3.183 cd/m2 1 footlambert = (1/p) cd/ft2 = 3.426 cd/m2 1 candela/ft2 = 10.76 cd/m2 1 candela/in.2 = 1550 cd/m2 Illuminance 1 footcandle = 1 lm/ft2 = 10.76 lm/m2 or lx