Illuminance Converter
Convert lux, kilolux, foot-candles and phot — light falling on a surface, not the brightness of a source.
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- 27 categoriesFrom length to data storage
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How to use this tool
Steps for using the Unit Converter.
- Type a number into From — lux are preselected. Commas and scientific notation such as 2.5e3 are accepted.
- Pick the units to convert between; the result in foot-candles (or whichever unit you choose) updates as you type. Use the swap button to reverse the conversion.
- Set the decimal places, turn on Show formula to see the calculation, and copy or share the result.
- Below the converter, the table lists every illuminance unit with its exact definition, and the links open dedicated pages for the most common pairs.
Example
500 lux to foot-candles
500 lx46.45152 fc
Formula: fc = lx × 0.09290304Common use cases
- Lighting design and workplace standards.
- Photography and plant-growing light levels.
- Converting US foot-candle specifications to lux.
Illuminance unit table
| Unit | Symbol | System | Definition | In lux |
|---|---|---|---|---|
| Lux | lx | SI | 1 lumen per square meter | 1 |
| Kilolux | klx | Metric | 1,000 lx | 1,000 |
| Foot-candle | fc | US customary | 1 lumen per square foot ≈ 10.764 lx | 10.7639104167 |
| Phot | ph | Metric | 1 lumen per cm² = 10,000 lx (CGS) | 10,000 |
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- Radiation Dose converterµSv · mSv · Sv · mrem · rem
About illuminance units
Illuminance is the light falling on a surface, measured in lux (one lumen per square meter). It's the number a light meter gives and the one lighting standards specify, e.g. about 500 lx for office desks.
It isn't the same as luminous flux (the total light output of a source, in lumens) or luminance (how bright a surface or screen looks, in candela per square meter, “nits”). Those are different quantities and can't be converted to lux without knowing the geometry, so they aren't mixed in here. The foot-candle (one lumen per square foot ≈ 10.764 lx) is used in US lighting design.
Limitations
- Results are rounded for display only; the calculation keeps full precision (15 significant digits).
Frequently asked questions
How many lux is a foot-candle?
1 fc ≈ 10.764 lx.
Can I convert lumens to lux?
Only if you know the area the light falls on: lux = lumens ÷ m². They're different quantities.
Is lux the same as nits?
No. Lux measures light arriving at a surface; nits (cd/m²) measure the brightness of a surface or screen.
Are these illuminance conversions exact?
Each unit is defined from its official definition (for example 1 inch = 2.54 cm exactly). Results are calculated in double precision and only rounded to the decimal places you choose when shown.