Free · No login required
Lighting illuminance estimate
Estimate centre illuminance from candela and throw distance for a fixed luminaire setting.
On-axis luminous intensity (cd): 0–1000000000; Throw distance (m): 0.1–1000
Inputs stay on this page and clear on refresh.
Lighting illuminance estimate
On-axis luminous intensity (cd): 50500 Throw distance (m): 10
- Centre illuminance (lx)
- 505.000000
- Centre illuminance (fc)
- 46.916035
E = I/d² for normal incidence on the beam axis, with intensity in candela and distance in metres. Footcandles = lux × 0.09290304, using the exact international foot. Use manufacturer intensity for the same lens, focus, colour and output setting. Assumes far-field point-source behaviour and no obstruction; near-field optics, haze, losses, reflections and tilted surfaces are excluded. Centre lux is not average coverage or lumens, camera exposure, flicker or a safety criterion. Verify with photometric data and a meter.
Methodology
How it works
E = I/d² for normal incidence on the beam axis, with intensity in candela and distance in metres. Footcandles = lux × 0.09290304, using the exact international foot. Use manufacturer intensity for the same lens, focus, colour and output setting. Assumes far-field point-source behaviour and no obstruction; near-field optics, haze, losses, reflections and tilted surfaces are excluded. Centre lux is not average coverage or lumens, camera exposure, flicker or a safety criterion. Verify with photometric data and a meter.
Method and assumptions documented by Techrider.live
2026-10-24
Frequently asked questions
Does doubling the throw halve the lux?
No. At a fixed setting, twice the distance gives one quarter of the centre lux. For example 50,500 cd at 10 m gives 505 lx. Do not infer whole-beam uniformity from the centre value.