Photometric & Optics
Lux at Distance Calculator
Calculate point illuminance using the inverse square law with cosine angle correction. Enter luminous intensity and geometry to find exact lux at any surface point.
Inputs
Luminous Intensity 1000 cd
Distance (d) 3.0 m
Angle of Incidence (θ) 0°
E = I · cos(θ) / d²
E = 1000 × cos(0°) / 3.0² = 111.1 lux
E = 1000 × cos(0°) / 3.0² = 111.1 lux
Geometry Diagram
111
lux (lx)
Illuminance E
10.3
fc
Foot-candles
Office task
Comparable to
300–500 lux typical
Illuminance reference scale (lux)
0.1105005k100k+
Moonlight
0.1–1 lx
Corridor
50–100 lx
Office task
300–500 lx
Surgery
10,000+ lx
Daylight
10–25k lx
Full sun
100,000 lx