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Illuminance Conversion
Tool Description
Illuminance Conversion is an online illuminance unit converter that supports mutual conversion between lux (lx), lumen per square meter (lm/m²), lumen per square centimeter (lm/cm²), phot (ph), foot-candle (fc), and nox (nx). Enter any value and unit to instantly view corresponding results in all other units, suitable for lighting design, photography, architectural standards, agricultural cultivation, and more.
How to Use
- Enter value
Input the value to convert in the input field, supporting integers and decimals, e.g.,
500,0.1 - Select source unit
Choose the illuminance unit of the current value from the dropdown list (lx/lm/m²/lm/cm²/ph/fc/nx)
- View results
Click the "Convert" button or press Enter, and the result area below will display corresponding values in all units, with a copy button on the right of each result for convenient use
Use Cases
- Lighting design: Indoor lighting standards are typically expressed in lux (lx), e.g., office desk illuminance requires 300~500 lx, while US/European documentation may use foot-candle (fc). Quickly convert between unit systems during the design phase
- Photography & videography: In studio lighting setups, light meter readings are often displayed in lx or fc. Photographers can quickly convert readings as needed to match exposure parameter requirements of different equipment
- Agricultural cultivation: In greenhouse supplemental lighting and plant factories, illuminance is a key parameter affecting crop growth. Different crops require different light intensities (e.g., leafy vegetables 5,000~10,000 lx). Use this tool to quickly compare light data in different units
Key Advantages
- Free with daily quota
This tool gives you free daily uses, enough for everyday light conversion needs. For higher volumes or more frequent use, a membership unlocks more quota.
- Local calculation
All conversions run entirely in your browser. Your input never leaves your device, keeping your data private.
- Easy to use
Just enter a value and pick a unit, then one click shows all target results. Enter key is also supported for quick conversion.
- Comprehensive units
Supports lx, lm/m², lm/cm², ph, fc, nx and other common illuminance units, covering lighting design, photography, agriculture and more.
- High precision
Uses exact conversion factors with double-precision floating-point math, keeping enough decimals for professional and daily needs.
- Cross-platform
The responsive layout works smoothly on phone, tablet and desktop, so you can convert illuminance anytime, anywhere.
Illuminance Unit Conversion Relationships
The following shows the conversion relationships between illuminance units, with lux (lx) as the base unit:
| Unit Name | Abbreviation | Conversion Relationship | Equivalent lx |
|---|---|---|---|
| Lux | lx | 1 lx = 1 lm/m² | 1 |
| Lumen per Square Meter | lm/m² | 1 lm/m² = 1 lx | 1 |
| Lumen per Square Centimeter | lm/cm² | 1 lm/cm² = 10,000 lx | 10,000 |
| Phot | ph | 1 ph = 10,000 lx | 10,000 |
| Foot-Candle | fc | 1 fc = 1 lm/ft² | 10.7639104167 |
| Nox | nx | 1 nx = 0.001 lx | 0.001 |
Common Environmental Illuminance Reference Values
The following shows the illuminance ranges of common environments in daily life for reference comparison:
| Environment | Illuminance |
|---|---|
| Full moon night | 0.0001 lx |
| Street lighting | 1 lx |
| Home living room | 50 ~ 100 lx |
| Office desk | 200 ~ 500 lx |
| Precision workshop / Operating room | 500 ~ 1,000 lx |
| Overcast outdoor | 10,000 ~ 25,000 lx |
| Sunny outdoor (shade) | 32,000 ~ 100,000 lx |
| Summer noon direct sunlight | ~ 100,000 lx |
The Historical Origins of Phot and Lux
Phot (symbol ph) is an illuminance unit in the centimeter-gram-second (CGS) system, defined as the illuminance produced by 1 lumen uniformly distributed over 1 square centimeter. 1 ph = 1 lm/cm² = 10,000 lx. The phot was common in early lighting engineering literature but has largely been replaced by the SI unit lux.
Nox (symbol nx) is a smaller illuminance unit, 1 nx = 0.001 lx = 1 mlx (millilux). Nox is commonly used for measuring low-light environments such as night vision device testing, darkroom operations, and astronomical observations. Note that 1,000 nx = 1 lx.
FAQ
Lux (symbol lx) is the standard unit of illuminance in the International System of Units (SI), defined as the illuminance produced by 1 lumen (lm) of luminous flux uniformly distributed over 1 square meter (m²), i.e., 1 lx = 1 lm/m². Illuminance measures the total amount of visible light received per unit area, and is the most commonly used metric in lighting design, photography, and architectural standards.
Lumen (lm) is the unit of luminous flux, representing the total amount of visible light emitted by a source; lux (lx) is the unit of illuminance, representing the luminous flux received per unit area. The relationship is: 1 lx = 1 lm/m². For example, a 1,000 lm light source illuminating a 1 m² surface produces about 1,000 lx on that surface; if the same source illuminates a 10 m² surface, the illuminance drops to about 100 lx. Luminous flux is "how much light is emitted," while illuminance is "how bright a certain area is."
1 fc ≈ 10.76391 lx. Foot-candle (symbol fc) is an imperial illuminance unit, defined as the illuminance produced by 1 lumen uniformly distributed over 1 square foot, i.e., 1 fc = 1 lm/ft². Since 1 m² = 10.76391 ft², 1 fc = 10.76391 lx. Conversely, 1 lx ≈ 0.0929 fc. Foot-candle is still widely used in the US lighting industry.
According to China's national standard "Standard for Lighting Design of Buildings" (GB 50034), the standard illuminance for office desks is 300~500 lx (approximately 28~46 fc), classroom desks require 300 lx, and precision workplaces (such as precision assembly, operating rooms) need 750~1,500 lx or higher. Corridors and stairways generally require 50~100 lx. European and North American standards have similar values but typically use fc as the unit; use this tool for quick conversion.
No. All conversion calculations are performed entirely in your browser locally using pure JavaScript math. Your input data never leaves your device, so please feel free to use it.
This tool uses JavaScript double-precision floating-point numbers (64-bit IEEE 754) for calculations, which is sufficiently accurate for most everyday scenarios. The foot-candle conversion uses a high-precision coefficient of 1 fc = 10.7639104167 lx. Up to 6 significant decimal places are retained, with excess digits automatically truncated. For extremely large or small values, minor errors may occur due to floating-point precision limits, but this has virtually no impact in practical applications.
Free daily quota. This tool gives you free daily uses, enough for everyday light conversion needs. For higher volumes or more frequent use, a membership unlocks more quota.
No registration needed. Just open the page and enter a value to convert. Some advanced benefits require a member account.
Yes. The responsive layout adapts to phone, tablet and desktop. Open it in a mobile browser to convert and copy results smoothly.
1 fc is much larger than 1 lx. 1 foot-candle (fc) is about 10.76 lux (lx). For a quick estimate, if a value is given in fc, use roughly "lx ≈ fc × 10.76"; this tool gives the exact value.
Ready to use, focused on conversion. A light-meter app measures; this tool converts units. Open the page to switch measured values between units, no professional software needed, ideal for on-site quick checks.
Check your input first. Make sure you entered a valid number, not empty or invalid characters. If it still fails, refresh the page and try again; extremely large or small values may show minor floating-point errors but do not affect daily use.
Content last updated：2026-07-16
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