Lux to Footcandles Conversion Calculator
Convert illuminance from lux (lx) to footcandles (fc). Enter the illuminance in lux and press Calculate to get footcandles using Ev(fc) = Ev(lx) × 0.09290304 = Ev(lx) / 10.76391. Everything runs locally in your browser.
Enter the illuminance in lux
Type the illuminance Eᵥ in lux (lx) — for example, a well-lit office is around 500 lx and direct sunlight reaches about 100,000 lx. Only digits and an optional decimal point are accepted; negatives and non-numeric text are rejected.
Press Calculate
The footcandle value appears in the read-only result field, computed with exact decimal arithmetic as lux × 0.09290304 and rounded (half-up) to at most 8 decimal places. 500 lx gives 46.45152 fc.
Read the result or reset
Select the value in the result field to copy it yourself. Press Reset to clear the input and the result and start a new conversion. An in-app message tells you exactly what is wrong if a submit is invalid.
Lux to footcandles calculation
- Lux to footcandles formula
- The illuminance Eᵥ in footcandles (fc) is equal to the illuminance Eᵥ in lux (lx) times 0.09290304: E(fc) = E(lx) × 0.09290304 = E(lx) / 10.76391. One footcandle is one lumen per square foot, and one lux is one lumen per square meter — the factor is the square of the foot-to-meter ratio.
- Worked examples
- A 500 lx office gives 500 × 0.09290304 = 46.45152 fc. A 1,000 lx studio gives 92.90304 fc. Direct sunlight at about 100,000 lx is 9,290.304 fc. Exactly 10.76391 lx corresponds to about 1 fc (this calculator shows 0.99999996 fc because it multiplies by the exact 0.09290304 constant).
- Lux vs footcandles
- Both units measure illuminance — luminous flux per area reaching a surface. Lux is metric (lm/m²) and is used worldwide; the footcandle (lm/ft²) is still common in North American lighting practice, architecture, and film. Converting between them never changes the physical light level, only the unit it is stated in.
- How are results rounded?
- The product lux × 0.09290304 is computed exactly in decimal (no floating-point drift), then rounded half-up to at most 8 decimal places with trailing zeros trimmed. Zero input displays 0 fc.
- What inputs does the calculator reject?
- Empty input, non-numeric text, scientific notation such as 5e2, comma thousands separators, negative illuminance (it cannot be physically negative), and values of 10¹² lux or above, which are far beyond any real lighting condition. An error message appears under the field and the result field stays empty until a valid submit.
Converting the other way? Use the footcandles to lux calculator.
Privacy: every calculation runs in your browser tab — no value you type is sent anywhere. Conversions assume the standard photometric definitions; verify real lighting installations with a calibrated lux meter.