💡 Illuminance Conversion Calculator 2026
Convert between lux, footcandles, phots, and other light measurement units
500 lx = 46.45 fc
Formula: value × 0.0929
📊 All Conversions
Common Illuminance Conversions
| From | To | Multiply by |
|---|---|---|
| 1 lux (lx) | footcandle (fc) | 0.0929 |
| 1 footcandle (fc) | lux (lx) | 10.764 |
| 1 phot (ph) | lux (lx) | 10,000 |
| 1 lux (lx) | lumen/m² | 1 (same) |
| 1 footcandle | lumen/ft² | 1 (same) |
| 1 nox | lux | 0.001 |
Typical Illuminance Levels
| Environment | Lux | Footcandles |
|---|---|---|
| ☀️ Direct sunlight | 100,000 | 9,290 |
| 🌤️ Overcast day | 1,000–2,000 | 93–186 |
| 🏢 Office lighting | 300–500 | 28–46 |
| 🏠 Living room | 50–300 | 5–28 |
| 🌙 Full moon | 0.1–0.3 | 0.01–0.03 |
| ⭐ Starlight | 0.0001 | 0.00001 |
| 📸 Photography studio | 500–1,000 | 46–93 |
| 🏥 Operating room | 10,000+ | 930+ |
Understanding Illuminance
💡 Lux (lx)
SI unit of illuminance. 1 lux = 1 lumen per square meter. Measures light falling on a surface. Used internationally for lighting design.
🇺🇸 Footcandle (fc)
Imperial unit. 1 fc = 1 lumen per square foot ≈ 10.764 lux. Common in US lighting industry. "Candle at one foot distance" origin.
🔬 Phot (ph)
CGS unit. 1 phot = 10,000 lux. Very bright — rarely used today. Historical unit from early photometry.
📐 Lumens vs Lux
Lumens = total light output. Lux = light per area. A 1000 lumen bulb gives different lux depending on room size/distance.
Frequently Asked Questions
What is illuminance?
Illuminance is the amount of light (luminous flux) falling on a
surface per unit area. It measures "how bright" a surface is illuminated, not how bright it appears
(that's luminance).
How do I convert lux to footcandles?
Divide by 10.764 or multiply by 0.0929. Formula: fc = lux ×
0.0929. Example: 500 lux = 46.45 footcandles.
How do I convert footcandles to lux?
Multiply by 10.764. Formula: lux = fc × 10.764. Example: 50
footcandles = 538 lux.
What is the difference between lux and lumens?
Lumens measure total light output from a source.
Lux measures light per area. 1000 lumens in 1 m² = 1000 lux. Same lumens in 10 m² = 100
lux.
What is a footcandle?
1 lumen per square foot. Originally, illumination from a standard
candle at 1 foot distance. 1 fc ≈ 10.764 lux. Used primarily in North America.
What is a phot?
CGS unit = 10,000 lux = 1 lumen/cm². Very bright — direct sunlight
is ~10 phots. Rarely used today; lux is preferred.
What lux level is recommended for offices?
300-500 lux for general office work. 500-750 lux for detailed
tasks. 200-300 for corridors. Check local building codes for requirements.
How many lux is direct sunlight?
~100,000 lux on a clear day. Varies with sun angle, clouds,
location. Overcast day: 1,000-2,000 lux. Shade on sunny day: 10,000-25,000 lux.
What is nox?
1 nox = 0.001 lux = 1 millilux. Used for very low light levels
like starlight or moonless nights. "Nox" is Latin for night.
How is illuminance measured?
With a lux meter (light meter). The sensor measures light falling
on its surface. Position matters — measure at work surface, not ceiling.
What lux is needed for reading?
300-500 lux minimum for comfortable reading. 500+ for detailed
work or older eyes. Too bright (>1000) causes glare and eye strain.
How does distance affect illuminance?
Inverse square law: Double the distance = 1/4 the illuminance.
Light spreads over larger area. E = I/d² where I is intensity, d is distance.
What is the difference between illuminance and luminance?
Illuminance (lux) = light falling ON surface.
Luminance (cd/m²) = light reflected FROM surface. Illuminance is incident; luminance is
perceived brightness.
What lux do plants need?
Varies by plant: Low light plants: 500-2,500 lux. Medium:
2,500-10,000. High light/vegetables: 10,000-50,000. Measure during photoperiod.
How do I calculate required lumens from lux?
Lumens = Lux × Area (m²). Need 500 lux in 20 m² room? 500 × 20 =
10,000 lumens total. Divide by bulb efficiency for number of bulbs.
What is metercandle?
Old name for lux. 1 metercandle = 1 lux = illumination from 1
candle at 1 meter. Term rarely used today; lux is standard.
How accurate is this illuminance converter?
Uses exact conversion factors. Results are mathematically precise.
For lighting design, actual measurements depend on fixture placement, reflections, etc.