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Brightness Conversion
Tool Description
Brightness Conversion is an online luminance unit converter that supports mutual conversion between candela per square meter (cd/m², also known as nit), candela per square centimeter (cd/cm², also known as stilb sb), candela per square foot (cd/ft²), candela per square inch (cd/in²), foot-lambert (fL), lambert (L), and apostilb (asb). Enter any value and unit to instantly view the corresponding results in all other units. Suitable for display device evaluation, lighting design, photography and videography, optical research, and more.
How to Use
- Enter a value
Enter the luminance value to convert in the input field, supporting integers and decimals, e.g.,
500or0.1 - Select source unit
Choose the luminance unit of your value from the dropdown (cd/m², cd/cm², cd/ft², cd/in², fL, L, asb)
- View results
Click the Convert button or press Enter, and the result area below will display the corresponding values in all units, with a copy button on the right of each result for easy use
Use Cases
- Display Device Evaluation: Screen brightness parameters for phones, monitors, and TVs are typically labeled in cd/m² (nit), such as iPhone peak brightness up to 2,000 nits, while professional monitor brightness standards are often expressed in fL. Use this tool to quickly convert between different unit systems.
- Lighting & Optical Design: Luminance design for luminaires (luminous intensity per unit area of the emitting surface) often involves units like L (lambert) and asb (apostilb). Light source manufacturers and optical engineers use this tool to switch and compare between different units.
- Photography & Film Production: Monitor and viewfinder brightness calibration commonly uses cd/m² or fL. Film projector screen brightness standards (e.g., SMPTE standard specifies cinema screen center brightness of 16 fL ≈ 55 cd/m²) can be quickly converted using this tool.
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 cd/m², cd/cm², cd/ft², cd/in², fL, L, asb and other common luminance units, covering display, lighting, film 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 luminance anytime, anywhere.
Luminance Unit Conversion Relationships
The following shows the conversion relationships between luminance units, with candela per square meter (cd/m²) as the base unit:
| Unit Name | Abbr. | Conversion Relationship | Equivalent cd/m² |
|---|---|---|---|
| Candela per Square Meter | cd/m² (nit) | 1 cd/m² = 1 nit | 1 |
| Candela per Square Centimeter | cd/cm² (sb) | 1 sb = 10,000 cd/m² | 10,000 |
| Candela per Square Foot | cd/ft² | 1 cd/ft² ≈ 10.7639 cd/m² | 10.7639104167 |
| Candela per Square Inch | cd/in² | 1 cd/in² ≈ 1,550 cd/m² | 1,550.0031 |
| Foot-Lambert | fL | 1 fL ≈ 3.426 cd/m² | 3.4262590996 |
| Lambert | L | 1 L ≈ 3,183 cd/m² | 3,183.0988618 |
| Apostilb | asb | 1 asb ≈ 0.3183 cd/m² | 0.3183098862 |
Common Display Device Luminance Reference
The following shows the conversion relationships between luminance units, with candela per square meter (cd/m²) as the base unit:
| Display Device | Luminance Range |
|---|---|
| Night sky / Starlight | 0.01 ~ 1 cd/m² |
| LCD monitor | 100 ~ 250 cd/m² |
| Smartphone screen | 300 ~ 600 cd/m² |
| Computer monitor / TV | 500 ~ 1,000 cd/m² |
| HDR display | 1,000 ~ 4,000 cd/m² |
| HDR professional monitor | 4,000 ~ 10,000 cd/m² |
| Sun surface luminance | ~ 1,600,000,000 cd/m² |
The History of Nit and Stilb
Nit is the informal name for the luminance unit candela per square meter (cd/m²), derived from the Latin word "nitere" (meaning "to shine"). 1 nit = 1 cd/m². Nit is widely used in the consumer electronics industry, such as phone screen brightness of 600 nits or TV peak brightness of 1,500 nits. Since nit is not an official SI name, cd/m² is typically used in academic and engineering literature.
Stilb (symbol sb) is the luminance unit in the centimeter-gram-second (CGS) system, defined as 1 cd/cm² = 10,000 cd/m². The stilb was common in early photometry literature but has largely been replaced by cd/m² (nit). Foot-lambert (fL) is an imperial luminance unit still widely used in the North American film and display industry. 1 fL = (1/π) cd/ft² ≈ 3.426 cd/m².
FAQ
Nit and candela per square meter (cd/m²) are different names for the same luminance unit: 1 nit = 1 cd/m². Candela per square meter is the standard SI unit of luminance, representing luminous intensity per unit area. Nit is the commonly used name in the consumer electronics industry. For example, a monitor labeled "300 nits" and "300 cd/m²" represents exactly the same brightness.
Luminance measures the luminous intensity emitted per unit area in a given direction, with units of cd/m² (nit), describing "how bright an object itself appears"; Illuminance measures the luminous flux received per unit area, with units of lx (lux), describing "how much light a surface receives". Simply put: luminance is the "output" of a light source or reflective surface, while illuminance is the "input" to an illuminated surface. For example, the light projected onto a screen by a projector is illuminance (lx), while the screen brightness perceived by the human eye is luminance (cd/m²).
1 fL ≈ 3.426 cd/m², 1 cd/m² ≈ 0.292 fL. Foot-lambert is an imperial luminance unit, defined as 1/π candela per square foot. In the North American film industry, cinema screen standard brightness is 16 fL (approximately 55 cd/m²). In monitor calibration, a common standard brightness of 100 cd/m² is approximately 29.2 fL. A rough memory aid: fL values are about 0.3 times cd/m² values.
Apostilb (symbol asb) is a smaller luminance unit, defined as the luminance of an ideal diffuse reflecting surface under 1 lx of illuminance, i.e., 1 asb = (1/π) cd/m² ≈ 0.3183 cd/m². Apostilb is primarily used for low-luminance measurements, such as night vision research and dark surface brightness measurements in astronomical observations. 1 cd/m² = π asb ≈ 3.1416 asb. Apostilb is still used in some European lighting standards and early photometry literature.
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. Foot-lambert and lambert conversions use high-precision coefficients such as 1 fL = 3.4262590996 cd/m² and 1 L = 3183.0988618 cd/m². 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.
Very simple.Enter the luminance value to convert, select its unit from the dropdown, click the Convert button or press Enter, and the result area will immediately list the converted values for all units (cd/m², cd/cm², cd/ft², cd/in², fL, L, asb). Each result has a copy button on the right to copy that value individually.
7 unit types in total.They include candela per square meter (cd/m²), candela per square centimeter (cd/cm²), candela per square foot (cd/ft²), candela per square inch (cd/in²), foot-lambert (fL), lambert (L), and apostilb (asb), covering display, lighting, and film scenarios.
No registration needed.This is a free online tool that works as soon as you open the page, without login or account binding. We provide free daily usage quota; light daily conversion needs can be met at zero cost, while higher quotas or more frequent use can be unlocked by becoming a member.
Yes.The page is responsive and works properly on phones, tablets, and desktop browsers. Conversion on mobile is also done locally, so you can use it anytime, anywhere without worrying about network transmission.
Different meanings.Luminance describes the luminous intensity per unit area of a light source or surface in a given direction, measured in cd/m² (nits), and is often used for screens and luminaires themselves. Illuminance describes the density of light flux received on a surface, measured in lux (lx), and is used for indoor lighting design. They measure different things: luminance is about "emitted", illuminance is about "received".
You will be prompted to re-enter.When the input is empty or non-numeric, the tool shows prompts like "Please enter a value" or "Please enter a valid number" and does not perform conversion. Only regular numeric values (integers, decimals, and scientific notation) are supported; letters, unit symbols, and other non-numeric content are not accepted. Please confirm the input is a pure number and try again.
Content last updated：2026-07-17
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