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Luminance Converter

Convert between candela per square metre (nit), stilb, foot-lambert, and lambert — the brightness of a surface, for displays and lighting.

Luminance

cd/m² (nit), stilb, foot-lambert

From
Result
0.0001

1 cd/m² = 0.0001 sb

Popular conversions

What Is a Luminance Converter?

A luminance converter translates how bright a surface appears between units — candela per square metre (nit) to foot-lamberts, stilb to nit. Luminance measures light emitted or reflected from a surface toward the eye, and the SI unit is the candela per square metre (cd/m²), commonly called the nit. It's the number behind display brightness specs, signage, and cinema screen standards.

This converter routes through the cd/m² (nit). The display industry quotes nits; cinema and older lighting use foot-lamberts; physics texts may use stilb or lambert. Since screen brightness ranges from a few hundred nits for a phone to thousands for an HDR TV, converting between these units is routine in display and lighting work.

This is one category of the full Unit Converter — pair it with our percentage calculator or scientific calculator for related everyday maths.

How Luminance Conversion Works

Everything routes through cd/m² (nit)

Each unit has a fixed nit factor. The converter normalises to cd/m², then projects to foot-lamberts, stilb, and lambert.

Nit = candela per square metre

1 nit = 1 cd/m². It measures luminous intensity per area of a surface — directly how bright that surface looks.

Foot-lambert for projection

A foot-lambert is the luminance unit of cinema and projection. 1 fL ≈ 3.426 cd/m²; SMPTE targets ~14 fL for film screens.

Luminance vs illuminance

Luminance is light leaving a surface (cd/m²); illuminance is light arriving on one (lux). Brightness of a screen vs lighting on a desk.

Core Luminance Conversion Factors

Multiply to reach cd/m² (nit); divide to come back.

Foot-lambert → cd/m²

× 3.42626

One foot-lambert is 3.426 cd/m². Cinema screens target about 14 fL (48 cd/m²).

Stilb → cd/m²

× 10000

One stilb is 10,000 cd/m² — one candela per square centimetre (CGS).

Nit definition

nit = cd / m²

One nit is one candela of intensity per square metre of surface.

How to Use the Luminance Converter

  1. 1

    Enter the luminance value

    Type the brightness you want to convert — a display spec, a screen measurement, a projection level.

  2. 2

    Choose the 'from' unit

    Pick cd/m² (nit), foot-lambert, stilb, or lambert as your starting unit.

  3. 3

    Choose the 'to' unit

    Select the target unit, or swap the two to reverse direction.

  4. 4

    Read every unit at once

    The all-units table shows the luminance in nits, foot-lamberts, and stilb together.

Key Luminance Concepts

Candela per square metre (nit)

The SI unit of luminance. A phone is a few hundred nits; an HDR TV peaks at 1,000–4,000 nits; direct sun is ~1.6 billion nits.

Foot-lambert

A luminance unit used in cinema and projection. SMPTE specifies ~14 fL for film and ~48 nits for digital cinema screens.

Luminance vs illuminance

Luminance (cd/m²) is how bright a surface looks; illuminance (lux) is how much light falls on it. The converter handles luminance.

Perceived brightness

Human brightness perception is roughly logarithmic, so doubling nits doesn't look twice as bright — a key point in display calibration.

Real-World Luminance Conversions

📱

Phone screens

A phone peaks around 800–2,000 nits for outdoor visibility. Display specs are quoted in nits (cd/m²).

📺

HDR TVs

HDR content is mastered to 1,000–4,000 nits. TV brightness wars are fought in nits.

🎬

Cinema screens

Digital cinema targets ~48 cd/m² (14 fL). Projection brightness is specified in foot-lamberts.

🖥️

Monitors

A typical desktop monitor runs ~250–350 nits; pro reference displays calibrate to a set cd/m². Calibration uses nits.

🚧

Signage

Outdoor LED signs reach 5,000+ nits to stay visible in sunlight. Sign brightness is rated in nits.

☀️

Natural sources

A clear sky is ~8,000 cd/m²; the Sun's disc ~1.6 × 10⁹. Luminance spans an enormous range across nits and stilb.

Best Practices for Luminance Conversion

  • ✓Use nits for displays. The display industry standardises on cd/m² (nits). Convert foot-lamberts and stilb to nits when comparing modern screen specs.
  • ✓Use foot-lamberts for projection. Cinema and projection standards (SMPTE) are written in foot-lamberts. Convert to fL when working to those specs.
  • ✓Keep luminance and illuminance distinct. cd/m² (from a surface) and lux (onto a surface) answer different questions. Don't convert one as if it were the other.
  • ✓Remember perception is non-linear. Brightness perception is roughly logarithmic, so a 2× nit increase isn't a 2× perceived jump. Useful when interpreting display numbers.
  • ✓Mind ambient conditions. Required luminance depends on ambient light — a screen needs far more nits in sunlight than in a dark room. Convert, then judge in context.

Common Luminance Conversion Mistakes

Confusing luminance with illuminance

cd/m² (surface brightness) and lux (light on a surface) are different quantities. Mixing them misjudges either a display or room lighting.

Mishandling foot-lambert factor

1 fL ≈ 3.426 cd/m². Using the wrong factor throws off projection-brightness calculations against cinema standards.

Treating nits as lumens

Lumens measure total output; nits measure surface brightness per area. A high-lumen projector on a huge screen can still be low in nits.

Assuming linear perception

Doubling nits doesn't double perceived brightness. Reading nit figures as linear brightness overstates differences.

Why Luminance Conversion Matters

Luminance is the headline number for displays, projection, and signage — phones, TVs, monitors, and LED boards all compete on nits, while cinema works in foot-lamberts. Converting between them, and not confusing luminance with the lux of illuminance or the lumens of total output, is essential for spec comparisons and calibration.

As HDR and high-brightness outdoor displays push luminance ever higher, accurate units underpin standards compliance and honest marketing alike. A converter that routes through cd/m² and surfaces foot-lamberts and stilb lets display engineers, cinema technicians, and AV professionals compare brightness across every convention in use.

Built for display and AV engineers, cinema technicians, and signage professionals converting between nits, foot-lamberts, and stilb.

Linear unit factors follow the BIPM SI brochure, the NIST Guide to the SI, and ISO 80000. Currency rates load live from open.er-api.com; crypto prices from CoinGecko. See our methodology and editorial policy. Educational only — not certified for regulated trading, settlement, medical, or aerospace use.

Luminance Converter FAQs

A nit is the common name for the candela per square metre (cd/m²), the SI unit of luminance — how bright a surface appears. A typical phone display runs a few hundred nits, an HDR TV peaks at 1,000–4,000 nits, and direct sunlight is around 1.6 billion nits.

Multiply foot-lamberts by 3.426 to get nits (cd/m²). So a cinema screen at 14 fL is about 48 nits. Foot-lamberts are used in projection and cinema standards (SMPTE), while displays are specified in nits, so this conversion bridges the two industries.

Luminance (cd/m² or nits) measures how bright a surface appears — the light it emits or reflects toward your eye. Illuminance (lux) measures how much light falls onto a surface. A TV's brightness is luminance; the lighting on your desk is illuminance. They're related but answer different questions.

HDR content is typically mastered to peak brightness of 1,000 to 4,000 nits, so HDR-capable TVs aim for at least 600–1,000 nits to render highlights convincingly. SDR content and most monitors sit lower, around 250–350 nits. The right figure depends on ambient light and content.

Luminance is the measured, physical quantity (cd/m²); 'brightness' is the subjective perception of it, which is roughly logarithmic. Doubling luminance does not double perceived brightness, which is why display calibration distinguishes the measured nits from how bright a screen actually looks.

It uses exact and standard factors (1 foot-lambert = 3.4262591 cd/m², 1 stilb = 10,000 cd/m²) and routes every conversion through the candela per square metre at full precision, so the result is exact to your input precision.

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