Method and source check
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Editorial check of method and sources; this is not professional review or advice.
Method
The calculator converts square feet to square metres when necessary, divides luminous flux by illuminated area to obtain lux, and also reports the equivalent average illuminance in foot-candles.
lux = lumens / area in m²
foot-candles = lumens / area in ft²
1 ft² = 0.092903 m²
Variables and units
- lm
- luminous flux in lumens
- lx
- illuminance in lumens per square metre
- fc
- illuminance in lumens per square foot
Worked example
For 1,000 lm distributed over 10 m², illuminance is 1,000 / 10 = 100 lx, equivalent to about 9.29 foot-candles.
Limitations
Lux and foot-candles are each rounded to at most two decimal places. The result card displays the rounded numbers without trailing zero padding.
- This is an average-area calculation that assumes the entered luminous flux reaches the surface uniformly. It does not model distance, beam angle, fixture losses, reflections, obstructions, or compliance with a lighting standard.
- Input 1,000 lm over 10 m² returns 100 lx and 9.29 foot-candles.
- Input 1,000 lm over 100 ft² returns 107.64 lx and 10 foot-candles, using 0.092903 m² per ft².
- Zero or negative lumens or area fails validation; either area unit requires a strictly positive area.