Luminance Converter

Convert non-negative luminance between cd/m², nit, cd/cm², stilb, apostilb, lambert, cd/ft², cd/in², and foot-lambert for displays and photometry.

Photometry

Convert luminance across display, CGS, and legacy cinema units

Restate a measured or specified luminance without confusing it with illuminance, luminous intensity, or total light output.

Quick presets

Scope note

This page converts luminance only. It does not estimate illuminance on a surface or derive screen brightness from ambient conditions, viewing geometry, or total luminous flux.

Enter values Provide a luminance value and source unit to calculate the full conversion sheet.

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Photometry

Luminance converter: cd/m², nit, foot-lambert, and legacy display-brightness units explained

A luminance converter rewrites the same photometric surface quantity in the unit your display specification, cinema calibration note, or lighting reference expects. That helps because luminance data appears in both SI forms such as cd/m² and field-specific labels such as nit or foot-lambert.

What luminance measures

Luminance describes luminous intensity per unit projected area in a given direction. It is the photometric quantity used for self-luminous screens, emitting surfaces, and reflected-surface reporting in display and lighting work.

The value can be written as cd/m², nit, foot-lambert, stilb, or related legacy units without changing the surface quantity being described.

L = d²I / (dA cos θ)

Shows luminance as directional intensity per projected area.

1 nit = 1 cd/m²

Links the common display-industry label to the SI-derived luminance unit.

1 fL ≈ 3.426 cd/m²

Shows the common cinema-screen conversion scale used by this page.

Why luminance is not the same as illuminance

Luminance describes the emitting or reflecting surface itself in a given direction. Illuminance describes light arriving on a surface. Those are different quantities, even though both appear in photometric workflows.

This page therefore stays with luminance units only and does not convert to lux, foot-candles, or viewing-condition estimates.

Why legacy labels still appear in practice

Display and cinema work often mix SI and older photometric labels. You may see `cd/m²` in standards documents, `nit` in consumer-display specifications, and `fL` in projection and cinema calibration notes.

The legacy labels remain useful for reading older references, but the converter keeps the SI base explicit so the photometric quantity stays clear.

Further reading

Frequently asked questions

Is a nit the same as cd/m²?

Yes. One nit is numerically equal to one candela per square metre.

 What is the difference between luminance and brightness?

Luminance is a measurable photometric quantity. Brightness is a visual perception term, so the two should not be treated as interchangeable in technical work.

 Can this page convert luminance to lux?

No. Lux is illuminance, which is a different photometric quantity. This page stays with luminance units only.

 Why does cinema work still use foot-lamberts?

Foot-lamberts remain common in older cinema and projection workflows, even though SI reporting increasingly uses cd/m².

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