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Lux to Foot-Candles Calculator

Convert an illuminance in lux into foot-candles, for reading a metric lighting level against a North American specification.

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  • Every formula cited
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SettingsSettings for this calculationUS
Market
Imperial · sales tax
The light level in lux, from a meter reading or a specification.

Illuminance is light arriving at a surface, so the figure only means something once you say which surface. Office levels are quoted at the working plane, normally 0.8 m above the floor; circulation levels at floor level; task levels at the task itself. A meter held at chest height in the middle of a room is measuring none of these three.

Illuminance

46.45 fc

High confidence

1 foot-candle = 1 lumen per square foot = 10.7639 lux. Exact by definition. State the plane the level applies to whenever you quote the converted figure.

Lux entered
500 lx
Foot-candles
46.45 fc
Lumens per square metre (the same thing)
500 lm/m²
Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

  • NIST SP 811, Appendix B — illuminance: 1 footcandle = 10.76391 lx
  • The lux is one lumen per square metre and the footcandle one lumen per square foot (SI Brochure, 9th edition, derived units)

Inputs used

Illuminance (lx)
500

Intermediate steps

Lux entered
500 lx
Foot-candles
46.45 fc
Lumens per square metre (the same thing)
500 lm/m²
Final result46.45 fc

Confidence note: 1 foot-candle = 1 lumen per square foot = 10.7639 lux. Exact by definition. State the plane the level applies to whenever you quote the converted figure.

Add the equipment this sizes

This result is a specification — 46.45 fc — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-09-12 · v1.0.0

Regulatory standards & verification citations2
  1. NIST SP 811, Appendix B — illuminance: 1 footcandle = 10.76391 lx
  2. The lux is one lumen per square metre and the footcandle one lumen per square foot (SI Brochure, 9th edition, derived units)
Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Lighting is specified in lux nearly everywhere except North America, and the fittings are traded globally, so the two scales meet constantly on the same job. The awkwardness is not the arithmetic but the fact that the round numbers in one system are untidy in the other: nobody writes a specification calling for 46 foot-candles, so a converted metric requirement always has to be read as a floor that a 50 fc design clears rather than as a target to hit. That is the reading this page is built for — a European or Australian level in hand, a North American photometric layout to check it against, and a need to know by how much the design passes rather than merely that it does.

Called something else where you work? Illuminance — the term in each market, how close the equivalence really is, and the standard that governs it.

How to calculate lux to foot-candles in 2 steps

  1. Illuminance (lx)The light level in lux, from a meter reading or a specification.
  2. IlluminanceThe tool computes the illuminance from those figures and shows the formula, its sources, and a confidence rating alongside it.

Lux to Foot-Candles at common values

Page defaults, not your figures above.

Illuminance (lx)Illuminance (fc)
504.65
1009.29
20018.6
50046.5
1,00092.9
2,000186
5,000465

Frequently asked questions

Why is the factor the same as the one for square feet?
Because it is that factor. A foot-candle is a lumen spread over a square foot and a lux is the same lumen spread over a square metre, so the only thing that changes between them is the area. Spread it over 10.7639 times the area and you get 10.7639 times fewer units of it.
How do typical levels compare between the two?
The round numbers do not line up, which is the practical difficulty. A 500 lux office is 46 fc, and North American practice calls the same room 50 fc, which is 538 lux. The two conventions are about eight per cent apart and neither market rounds to the other's grid.
Is this the same as lumens?
No, and it is the most common confusion in lighting. Lumens are what a fitting emits in total; lux and foot-candles are what lands on a surface. The same 3,000-lumen fitting gives a bright pool under it and very little four metres away, and only the illuminance figures describe that difference.
Does my phone's light meter app give a usable number?
For a rough comparison between two spots in the same room, often yes. For anything that will be checked against a specification, no — phone sensors are uncalibrated, have no cosine correction for light arriving at an angle, and respond differently to LED and daylight spectra.
Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.