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Professional Luminance Converter — 17 Units | Nits, Lamberts, Stilbs | ASLI FORM

Luminance Converter

Convert between candela per square meter (nits), lamberts, foot-lamberts, stilbs, apostilbs, skots, and 10+ other photometric luminance units with CIE-standard precision.

Conversion Formula
1 cd/m² = 1 nit

All 17 Luminance Units

SI, CGS, Imperial & Traditional

Common Conversions

Quick reference from 1 cd/m²
UnitSymbolEquals 1 cd/m²

Conversion Formulas

Exact mathematical relationships

All luminance conversions are based on the SI unit candela per square meter (cd/m²). The formulas below show exact relationships using π where applicable.

Real-World Applications

Luminance measurement is critical across many industries. Here's where these units are used in practice.

  • Display Technology TV, monitor, and smartphone brightness is measured in nits (cd/m²). HDR displays reach 1000+ nits.
  • Cinema & Projection Cinema screen brightness is measured in foot-lamberts (fL). SMPTE standard is 14 fL (48 cd/m²).
  • Photography & Lighting Light meters measure scene luminance to determine correct exposure settings for cameras.
  • Road & Street Lighting Road surface luminance is measured to ensure safe nighttime driving conditions per CIE standards.
  • Architectural Lighting Building codes specify minimum luminance levels for offices, hospitals, and public spaces.
  • Vision Science Skots and apostilbs are used in scotopic (night) vision research and low-light studies.
  • Astronomy Sky brightness and celestial object luminance are measured for light pollution studies.
  • Automotive Lighting Headlight and dashboard luminance are regulated for driver safety and comfort.

History of Luminance Units

Luminance measurement has evolved over centuries, from early photometric experiments to modern SI standardization.

  • 1760 — Bouguer & Lambert Pierre Bouguer and Johann Heinrich Lambert established the foundations of photometry.
  • 1860 — Stilb Introduced The stilb (cd/cm²) was introduced in the CGS system for scientific luminance measurement.
  • 1937 — CIE Standardization The International Commission on Illumination (CIE) standardized photometric units internationally.
  • 1948 — Candela Redefined The candela was redefined based on blackbody radiation at the freezing point of platinum.
  • 1979 — Modern Candela The candela was redefined in terms of monochromatic radiation at 540×10¹² Hz, the current definition.
  • 2000s — Nit Becomes Popular The term "nit" became widely used in consumer display marketing for screen brightness.

How to Use This Converter

Our luminance converter is engineered for photometric professionals, display engineers, and scientists. Follow these steps for accurate conversions.

  • Select Source Unit Choose the luminance unit you want to convert from (e.g., nits, lamberts, foot-lamberts).
  • Select Target Unit Choose the luminance unit you want to convert to from the second dropdown.
  • Enter Value Type your luminance value — the result appears instantly as you type.
  • View Formula The exact conversion formula is displayed below for verification and documentation.
  • Swap Units Click the swap button to instantly reverse the conversion direction.
  • Reference Table Use the common conversions table for quick lookups of standard values.

Frequently Asked Questions

Luminance is a photometric measure of the luminous intensity per unit area of light traveling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area within a given solid angle. The SI unit is candela per square meter (cd/m²), also called a nit. Luminance is measured using a luminance meter (spot photometer) that captures light from a specific viewing angle.
These three photometric quantities are often confused:
  • Luminance (cd/m²): Light emitted, reflected, or transmitted from a surface in a specific direction. What your eye perceives as "brightness."
  • Illuminance (lux): Light falling onto a surface. Measured with a light meter.
  • Luminous intensity (candela): Light emitted by a source in a specific direction, regardless of area.
In simple terms: intensity is about the source, illuminance is about what hits a surface, and luminance is about what leaves a surface toward your eye.
A nit is exactly equal to 1 candela per square meter (1 cd/m²). The term "nit" comes from the Latin word "nitere" meaning "to shine." It is widely used in consumer electronics to describe display brightness. For example, a typical smartphone screen has 500-1000 nits, while HDR TVs can reach 1000-2000+ nits.
One lambert (L) equals exactly 10,000/π cd/m², which is approximately 3,183.099 nits. The lambert is a CGS unit named after Johann Heinrich Lambert, the 18th-century mathematician who pioneered photometry. It represents the luminance of a perfectly diffusing surface emitting one lumen per square centimeter.
A foot-lambert (fL) equals 1/π candela per square foot, or approximately 3.426 cd/m². It is primarily used in the United States cinema industry to measure screen brightness. The SMPTE (Society of Motion Picture and Television Engineers) standard for cinema screens is 14 fL (48 cd/m²). It is also used in aviation for cockpit display brightness specifications.
A stilb (sb) is a CGS unit of luminance equal to 1 candela per square centimeter, or 10,000 cd/m². The name comes from the German word "still" meaning "shiny." One stilb represents the luminance of a surface emitting one candela per square centimeter. While rarely used today, it appears in older scientific literature and some European standards.
An apostilb (asb), also called a blondel, equals 1/π cd/m² (approximately 0.3183 cd/m²). It represents the luminance of a perfectly diffusing surface that emits or reflects one lumen per square meter. The apostilb is useful in lighting engineering when working with Lambertian (perfectly diffusing) surfaces.
A skot (sk) equals 10⁻³ apostilbs, or approximately 3.183 × 10⁻ cd/m². The name comes from the Greek word "skotos" meaning darkness. Skots are used to measure very low luminance levels encountered in scotopic (night) vision conditions, such as starlight, moonlight, and dark-adapted human vision research.
A bril is an extremely small unit of luminance equal to 10⁻¹¹ cd/m². It is used in specialized vision science research to measure the absolute threshold of human vision — the minimum luminance detectable by the dark-adapted human eye. One bril represents an almost imperceptibly faint light source.
Typical smartphone screen brightness ranges from:
  • Standard use: 400-600 nits
  • Outdoor/HDR: 800-1200 nits
  • Peak HDR: 1500-2500 nits (flagship phones)
  • Auto-brightness max: 1000-1600 nits
For comparison, a typical office environment has ambient luminance of about 100-300 cd/m², and direct sunlight can exceed 10,000 cd/m².
Yes. Our converter uses scientifically-verified conversion factors from the International System of Units (SI) and CIE (International Commission on Illumination) standards. Results are accurate to 10 significant digits, which is more than sufficient for photometric engineering, display calibration, cinema standards compliance, and scientific research. For units involving π (lambert, foot-lambert, apostilb), we use the mathematical constant π to full floating-point precision.
Yes, the ASLI FORM Luminance Converter is 100% free forever. No registration, no usage limits, no hidden fees, and no advertisements. All calculations happen locally in your browser, so it works offline after the initial page load. Your privacy is completely protected — we do not collect or transmit any data.

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