Nit to Candela/m² Converter
Quickly convert from Nit to Candela/m².
How to convert
Formula:
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Photometric units quantify light as perceived by the human eye, weighting physical radiant power by the eye's spectral sensitivity.
Where is it used?
• Display & Consumer Electronics — Monitor, TV, smartphone, and projector brightness is specified in nits (cd/m²). HDR televisions target 1,000–10,000 nits; a typical laptop screen is 300–500 nits.
Examples:
• 1 cd/m² (nit) = 1 nit = 0.2919 footlambert
• 1 footlambert (fL) = 3.4263 cd/m²
Photometric units quantify light as perceived by the human eye, weighting physical radiant power by the eye's spectral sensitivity. Engineers, architects, display designers, and lighting professionals rely on photometric conversions between candela per square meter (cd/m²), nits, footlamberts, and stilbs to specify, measure, and compare luminance across different industries and standards.
Photometry is the science of measuring light in terms of its perceived brightness to the human eye. The key photometric quantity for surface brightness is luminance — the luminous intensity emitted per unit projected area. The SI unit is the candela per square metre (cd/m²), commonly called the nit in display and television industries. Related units include the footlambert (fL) used in US cinema, the stilb (sb, 1 cd/cm²) and the apostilb (asb). Luminance differs from illuminance (lux): luminance describes how bright a surface appears; illuminance describes how much light falls on it.
Where is it used?
- Display & Consumer Electronics — Monitor, TV, smartphone, and projector brightness is specified in nits (cd/m²). HDR televisions target 1,000–10,000 nits; a typical laptop screen is 300–500 nits.
- Cinema & Digital Projection — The US cinema industry specifies screen luminance in footlamberts (fL); the DCI (Digital Cinema Initiatives) standard requires 14 fL ≈ 48 cd/m² for 2D, 7 fL for 3D.
- Architectural & Road Lighting — Road surface luminance (cd/m²) is specified in lighting design standards (EN 13201) to ensure driver visibility at night.
- Automotive — Dashboard displays, head-up displays, and exterior lighting are characterised by luminance to ensure visibility in both bright sunlight and darkness.
- Medical Imaging — Diagnostic display monitors for radiology (X-ray, MRI) are calibrated to specific luminance levels (DICOM GSDF standard) to ensure consistent image interpretation.
Common Conversion Mistakes
Confusing luminance (cd/m²) with illuminance (lux)
Luminance (cd/m²) describes how bright a surface looks — it is measured looking at the surface. Illuminance (lux) describes how much light hits a surface — it is measured at the surface. A white desk lit to 500 lux may have a luminance of ~140 cd/m² (for a Lambertian reflector with 88% reflectance). They are fundamentally different quantities.
Forgetting the nit is not an SI named unit
The nit is an informal name for cd/m² used in the display industry. It is not an official SI unit but is universally understood in consumer electronics. 1 nit = 1 cd/m² exactly — no conversion factor needed.
Mixing up luminous and radiant quantities
Photometric units (lm, cd, lux, cd/m²) are weighted for human vision. Radiometric units (W, W/sr, W/m², W/(sr·m²)) measure physical power. They are related by the luminous efficacy of radiation (683 lm/W at 555 nm). Never mix photometric and radiometric values without conversion.
Ignoring angular and geometric factors in luminance calculations
Luminance is per steradian and per projected area, not per actual surface area. For a Lambertian (perfectly diffuse) surface, luminance L = E × ρ / π, where E is illuminance, ρ is reflectance. Omitting the π factor is a very common error in lighting calculations.
Quick Reference Table
| From | To |
|---|---|
| 1 cd/m² (nit) | 1 nit = 0.2919 footlambert |
| 1 footlambert (fL) | 3.4263 cd/m² |
| 1 stilb (sb) | 10,000 cd/m² |
| 1 apostilb (asb) | 1/π cd/m² ≈ 0.3183 cd/m² |
| 1 lambert (L) | 3,183.1 cd/m² |
| Typical laptop screen | 300–500 cd/m² |
| DCI cinema screen (2D) | ~48 cd/m² (14 fL) |
| Direct sunlight | ~1,600,000,000 cd/m² |
Frequently Asked Questions
What is a nit and why is it used for displays?
A nit is an informal name for candela per square metre (cd/m²), the SI unit of luminance. It became popular in the display industry because specifying brightness in cd/m² is more intuitive than saying 'luminous intensity per unit projected area.' Modern HDR displays range from 400 nits (entry HDR) to 10,000 nits (high-end OLED/MicroLED), compared to ~200 nits for a typical SDR monitor.
What is the difference between luminance and illuminance?
Illuminance (lux or fc) measures light arriving at a surface — it tells you how well-lit a room is. Luminance (cd/m²) measures light leaving a surface toward the observer — it tells you how bright the surface appears. A mirror and matte white paper can have the same illuminance (500 lux each) but vastly different luminances: the mirror concentrates reflected light into a narrow cone, producing very high luminance in one direction.
How do I convert between footlamberts and cd/m²?
1 footlambert = 1/π candela per square foot = 3.4263 cd/m². Conversely, 1 cd/m² = 0.2919 fL. The cinema standard of 14 fL ≈ 14 × 3.4263 ≈ 48 cd/m². For quick conversion: multiply fL by 3.43 to get cd/m², or multiply cd/m² by 0.292 to get fL.
What luminance level is comfortable for reading?
Display luminance for comfortable reading depends on ambient light. In a typical office (500 lux ambient), a monitor at 100–200 cd/m² with appropriate contrast ratio (≥ 4.5:1 for WCAG AA text) is comfortable. In a dark room, 80–120 cd/m² avoids eye strain. Outdoor use may require 700–1,000+ cd/m² to overcome sunlight glare.
Sources & Standards
- CIE (International Commission on Illumination) — Photometry standards
- ISO 9241-300 series — Ergonomics of visual displays
- Digital Cinema Initiatives (DCI) Specification v1.4
- Illuminating Engineering Society (IES) Lighting Handbook
Reviewed by The Unit Hub Editorial Team · March 2026