Footcandles to Lux Calculator
Convert illuminance from footcandles (fc), the imperial unit used in the United States, to lux (lx), the SI unit used everywhere else. Enter the illuminance in footcandles and press Calculate — the result comes from Ev(lx) = Ev(fc) / 0.09290304 = Ev(fc) × 10.76391. Everything runs locally in your browser.
Enter the illuminance in footcandles
Type the illuminance Ev in footcandles (fc) — the value from a light meter set to fc, or a lighting spec sheet. Zero or any positive value is accepted; zero footcandles gives zero lux.
Press Calculate
The illuminance in lux (lx) appears in the read-only result field: your input divided by 0.09290304 — exactly the number of square meters in one square foot. Press Calculate again after editing the value.
Read the result or reset
Results are shown with up to 12 significant digits (e.g. 1 fc = 10.7639104167 lx). Press Reset to clear the input, the result and any error message and start over.
Footcandles to lux conversion
- Footcandles to lux formula
- The illuminance Ev in lux (lx) is equal to the illuminance Ev in footcandles (fc) divided by 0.09290304: Ev(lx) = Ev(fc) / 0.09290304 = Ev(fc) × 10.76391. For example, 50 fc gives 50 / 0.09290304 ≈ 538.2 lx.
- What is 1 footcandle in lux?
- 1 fc = 10.76391 lx (exactly 10.7639104167… lx). A footcandle is one lumen per square foot; a lux is one lumen per square meter, and since 1 ft² = 0.09290304 m², the same light spread over a square meter reads about 10.76 times lower than over a square foot.
- Why divide by 0.09290304?
- Both units measure lumens per unit area — only the area unit differs. 0.09290304 is the exact number of square meters in one square foot (0.3048 m × 0.3048 m), so dividing by it is exact, not an approximation. The familiar × 10.76391 factor is just that division rounded to six decimals.
- fc and lx in real lighting specs
- U.S. lighting practice often quotes office desks at about 50 fc, while the same target appears as roughly 500 lx in metric specifications — a quick sanity check: multiply fc by about 10.76 and you should land near the metric figure.
- How accurate is this calculator?
- The conversion is a multiplication by an exact constant, computed with IEEE-754 double precision and shown with up to 12 significant digits, so rounding is far below any real light-meter resolution. Negative values are rejected because illuminance cannot be negative.
- Can I convert lux back to footcandles?
- Yes, algebraically: Ev(fc) = Ev(lx) × 0.09290304, e.g. 500 lx × 0.09290304 ≈ 46.45 fc. This page computes only the footcandles → lux direction.
Privacy: every calculation runs in your browser tab — no value you type is sent anywhere and nothing is stored after the tab closes. The converter changes units only; measurement quality depends on your light meter.