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How do I convert illuminance between lux and foot-candles?

Type a value into AnyTool Illuminance Converter and pick the units. It instantly converts both ways between lux (lx), kilolux, lumen per square metre, lumen per square foot, foot-candle (fc), phot, milliphot, nox and lumen per square centimetre, and shows the value in every unit at once in a copyable table. Everything is calculated in your browser, so nothing is uploaded.

  • Live two-way conversion — type in either field and the other updates
  • Exact foot-candle: 1 fc = 10.763910417 lux (lumens per square foot)
  • 1 lux = 1 lumen per square metre · 1 phot = 10,000 lux · 1 nox = 0.001 lux
  • See the value in every unit at once, each row copyable
  • 100% in your browser — no upload, no signup, works offline

What is

Illuminance Conversion

Illuminance is the amount of luminous flux (visible light) falling on a surface per unit area — one lux is one lumen spread over one square metre (lx = lm/m²). Illuminance conversion changes that figure from one unit to another, for example lux to foot-candles. Every illuminance unit relates to the SI base (the lux) by a single linear factor, so conversion is one multiply and one divide: a foot-candle is one lumen per square foot (10.763910417 lux), a phot is one lumen per square centimetre (10,000 lux), and a nox is one millilux (0.001 lux).

Converters

Related terms

lux to foot-candleslx to fcphotnoxlumen per square metre

Frequently Asked Questions

One foot-candle is 10.763910417 lux, so to convert lux to foot-candles multiply by about 0.0929.

One foot-candle (fc) equals 10.763910417 lux exactly, because it is one lumen spread over one square foot and one square foot is 0.09290304 square metres. To convert foot-candles to lux multiply by 10.763910417; to convert lux to foot-candles multiply by about 0.092903. For example, a well-lit office at 500 lux is roughly 46 foot-candles.

They are the same thing — one lux is defined as exactly one lumen per square metre.

Lux and lumen per square metre are identical units: 1 lx = 1 lm/m². Lux is the SI name for illuminance, the luminous flux (in lumens) falling on each square metre of a surface. Do not confuse it with the lumen, which measures the total light output of a source regardless of how far it spreads.

One phot is 10,000 lux, because it is one lumen per square centimetre.

One phot (ph) equals 10,000 lux — it is the CGS unit of illuminance, one lumen spread over one square centimetre, and there are 10,000 square centimetres in a square metre. The related nox is at the other extreme: one nox is one millilux (0.001 lux), a unit used for very low, near-darkness light levels.

No. Every calculation runs in your browser, so nothing is sent to a server and it works offline.

AnyTool Illuminance Converter computes every result locally in JavaScript using exact factors through a lux base. No value is uploaded, there is no tracking, and the page keeps working offline after the first load.

Detailed Explanation

Methodology

How the Illuminance Converter Works

AnyTool Illuminance Converter performs every calculation in the browser. Each unit declares a single linear factor relative to a shared lux base — the exact number of lux in one of that unit — so any unit converts to any other through the lux without an N-by-N table. The factors are the internationally-agreed definitions: a lux is one lumen per square metre (the base, 1), a kilolux is 1000 lux, and a lumen per square metre is identical to the lux. A foot-candle is one lumen per square foot, and because one square foot is exactly 0.09290304 square metres, one foot-candle is 1 / 0.09290304 = 10.763910417 lux exactly; the lumen per square foot shares that factor. The CGS phot is one lumen per square centimetre, which is 10,000 lux (there are 10,000 cm² in a square metre); the lumen per square centimetre shares that factor, and a milliphot is 10 lux. The nox, used for very low light, is one millilux (0.001 lux). A value is multiplied to lux and then divided into the target unit.

  • Nine units spanning SI, US/Imperial and CGS illuminance systems
  • The lux is the shared base; each unit is one exact factor
  • Foot-candle is exact: 1 fc = 10.763910417 lux (1 / 0.09290304)
  • 1 lux = 1 lumen per square metre; 1 phot = 10,000 lux; 1 nox = 0.001 lux
  • All arithmetic is client-side JavaScript — no server round-trip
How It Works

All Units, Precision and Reference

A single input is converted into every illuminance unit at once in a copyable table, with the source and target rows highlighted. A decimals control sets precision from 0 to 10 places, and magnitudes that are very large or very small automatically switch to scientific notation so results stay readable. A formula reference, a common-conversions list and a units-at-a-glance table (showing each unit in lux and which measurement system it belongs to) accompany the converter, plus everyday anchors such as a well-lit office at about 500 lux (≈ 46 foot-candles) and bright overcast-to-direct daylight at roughly 10,000–25,000 lux.

  • Convert-to-all table shows the value in every unit simultaneously
  • Each unit row is individually copyable
  • Adjustable precision from 0 to 10 decimal places
  • Automatic scientific notation for extreme magnitudes
  • Real-world anchors: office ≈ 500 lux, daylight ≈ 10,000–25,000 lux
Privacy & Security

Privacy and Offline Use

Because all conversion runs in the browser, no value is sent to a server, there is no account or tracking, and the page works offline after first load. The converter is built on a shared, unit-tested conversion engine that other AnyTool unit converters reuse, so behaviour is consistent across the site.

Illuminance conversion: in-browser (AnyTool) vs typical online converters
CapabilityAnyToolTypical online converters
ProcessingRuns in your browserOften server-side
Units9: lux, klx, lm/m², lm/ft², fc, phot, milliphot, nox, lm/cm²Often lux and foot-candle only
Factor accuracyExact definitions (1 fc = 10.763910417 lux)Frequently rounded to 10.76
Two-way inputEdit either field, both updateUsually one-direction with a button
All units at onceYes, copyable tableOften one target at a time
Works offlineYes (PWA)No
Cost / signupFree, no signupOften ad-heavy or gated

AnyTool converts every illuminance unit locally through an exact lux base and uploads nothing.