Illuminance Converter

Convert non-negative illuminance between lux, millilux, kilolux, foot-candle, phot, and nox for lighting, workplace, and display-viewing checks.

Photometry

Convert illuminance across lux, foot-candle, and legacy light-level units

Restate received light levels cleanly without mixing illuminance up with luminance, source intensity, or total lamp output.

Quick presets

Scope note

This page converts illuminance only. It does not estimate source output, room distribution, or exposure changes from distance, reflectance, fixture count, or beam geometry.

Enter values Provide an illuminance value and source unit to calculate the full conversion sheet.

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Photometry

Illuminance converter: lux, foot-candle, phot, and received-light units explained

An illuminance converter rewrites the same received-light level in the unit your lighting plan, workplace reference, display-viewing note, or historical photometry table expects. That matters because illuminance is not the same thing as luminance, brightness perception, or source luminous intensity.

What illuminance measures

Illuminance describes luminous flux incident on a surface per unit area. It is the photometric quantity used for task lighting, workplace targets, wayfinding levels, and surface-lighting checks.

The same received-light level can be written as lux, millilux, kilolux, foot-candle, phot, or nox without changing the quantity being described.

Ev = dΦv / dA

Defines illuminance as luminous flux per unit area on a receiving surface.

1 fc = 10.76391 lx

Shows the common imperial-to-SI relationship used in lighting references.

1 phot = 10,000 lx

Links the historical CGS unit to the SI illuminance scale.

Why illuminance is not the same as luminance or brightness

Illuminance is about light arriving at a surface. Luminance describes the emitting or reflecting surface in a given direction. Brightness is a perception term rather than a technical photometric unit.

This page therefore keeps the quantity limited to illuminance. It does not convert to display brightness labels, source-intensity units, or subjective viewing impressions.

Why legacy units still appear

Modern specifications usually prefer lux, but older literature and some field references still use foot-candles, phot, or nox. Converting those labels cleanly helps when comparing older guidance with current SI-based documentation.

The result table keeps lux as the explicit reference scale so workplace targets, lighting notes, and legacy references can be compared without blurring the quantity definition.

Further reading

Frequently asked questions

Is lux the same as foot-candle?

No. They measure the same quantity, illuminance, but on different scales. One foot-candle equals about 10.76391 lux.

 What is the difference between illuminance and luminance?

Illuminance measures light arriving on a surface. Luminance measures the light emitted or reflected by a surface in a given direction.

 Can this page convert brightness settings for a display?

No. Display brightness labels usually refer to luminance, not illuminance. This page stays with received-light units only.

 Why do phot and nox appear here?

They are legacy illuminance labels that still appear in older references, so keeping them available makes cross-checking historical material easier.

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