Illuminance converter
500 lux is 46.45152 foot-candles: move a light level between lux, foot-candles, phot and lumens per square metre when an office standard, an old facilities manual and your light meter each use a different scale. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Value
- 500
- Source unit of 'value'
- lx
- To
- fc
- Result
- 46.45152
- From label
- lux
- To label
- foot-candles
- Value lx
- 500
This illuminance converter turns a numeric lighting level from one common photometric unit into another and returns the converted magnitude with canonical unit labels. Conversion always bridges through lux using fixed SI and international factors, so the same input always yields the same result with no network calls, no sampling, and no date-dependent shortcuts. Typical checks include five hundred lux to foot-candles, one foot-candle to lux, and one phot to lux.
Where illuminance conversion fits in design, photography, and software
Building codes and office standards often quote recommended desk levels in lux while older North American facilities literature still lists foot-candles, so a single deterministic converter prevents hand-calculator drift when an architect, lighting designer, or facilities manager compares targets.
Photographers and videographers convert meter readings between lux and foot-candles when matching camera settings to a light meter that uses a different scale; museum and retail planners move between phot for dense display spots and lux for ambient gallery floors; teachers assign homework that needs a fast, offline check of foot-candles to lux without trusting opaque apps that silently change precision.
Developers call the same contract from scripts to seed deterministic test vectors for product UIs, to normalize user-entered workplace illuminance before sizing LED layouts, or to satisfy programming-challenge statements that demand exact SI factors rather than a hand-waved estimate. Product tools use the rewrite when a learner or agent types three hundred lux and the UI must show foot-candles and lumens per square meter side by side.
Pair it with luminous-flux tools when you need total lamp output first, and with the general multi-category unit converter when the same form must also handle length or temperature.
What you can do with it
Workplace and code compliance
Convert between lux and foot-candles when comparing office, classroom, or warehouse lighting targets across metric and imperial standards.
Photography and studio meters
Normalize light-meter readings between lux, foot-candles, and phot for deterministic exposure notes and set design worksheets.
FAQ
What does the illuminance converter cost?
It is free in your browser on this page.
What happens if I send an unknown unit?
Unknown or misspelled units are never silently mapped.
How many foot-candles is 500 lux?
500 lux is 46.45152 foot-candles. That is a typical desk level quoted in lux, shown in the foot-candles that older North American lighting literature still uses.
How many lux is one foot-candle?
One foot-candle is 10.763910416709722 lux. A foot-candle is one lumen on each square foot, and a square metre holds a little over ten square feet, so the same light gives a bigger number in lux.
What is a phot and when is it used?
A phot is 10,000 lux, a unit for very bright, concentrated light. Museum and retail planners use it for dense display spots and switch to lux for the ambient light on the gallery floor.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/conv/illuminance \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"value":500,"from":"lx","to":"fc"}'const res = await fetch("https://api.kit.forhosting.com/conv/illuminance", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"value": 500,
"from": "lx",
"to": "fc"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/illuminance",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"value": 500,
"from": "lx",
"to": "fc"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/illuminance", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"value":500,"from":"lx","to":"fc"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"value":500,"from":"lx","to":"fc"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/illuminance", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"value": 500,
"from": "lx",
"to": "fc"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.illuminance",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Limits
max_abs_value | 1000000000000000000 |
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Supported units are lux, foot-candles, phot, and lumens per square meter, plus everyday aliases such as lx, fc, ph, lm/m2, foot-candle, and luxes.
What the illuminance converter returns and which units it understands
An illuminance conversion answers a narrow question: given a light-level magnitude in one unit, what is the equivalent magnitude in another unit that people actually use for workplaces, classrooms, streets, and studio setups. This calculator accepts a numeric value, a source unit, and a target unit, then returns the converted result rounded to a stable precision, the canonical from and to identifiers, human-readable labels, the intermediate value in lux, and the SI factors used for the bridge. Canonical ids are lx for lux, fc for foot-candles, ph for phot, and lm_m2 for lumens per square meter. Everyday spellings such as lux, luxes, foot-candle, footcandles, foot candles, phot, lm/m2, lumen_per_square_meter, and lumens per square meter normalize to those ids so forms, query strings, and spreadsheets can reuse the same contract without inventing private enums. Lumens per square meter is definitionally identical to lux, so converting between lx and lm_m2 is a pure identity at any precision. There is no approximate sensor-calibration path and no CIE table lookup: the engine either multiplies and divides by fixed factors inside the supported magnitude range or rejects the input with invalid_input. Rejected cases include missing value, from, or to; non-finite numbers; magnitudes above the documented ceiling; and any unit string that is not on the supported list.
How factors are defined and how results stay reproducible
Optional scientific notation on the value string is allowed when it parses as a finite decimal; embedded spaces, hex prefixes, and non-numeric tokens are rejected with a clear message so a bad cell does not become a wrong lighting design number. Zero is a valid value and simply yields zero in the target unit. Computation multiplies value by the source factor in lux, then divides by the target factor: one lux is exactly one lumen per square meter; one foot-candle is one lumen per square foot, which equals ten point seven six three nine one zero four one six seven zero nine seven two two lux using the international foot; one phot is one lumen per square centimetre, which equals exactly ten thousand lux. The preferred fields are value for the illuminance magnitude, from for the source unit, and to for the target unit, with aliases amount, illuminance, n, quantity, and E for the value, unit, from_unit, source, and input_unit for from, and target, to_unit, output_unit, and into for to so heterogeneous clients can share one contract. An optional precision field, with aliases decimals and dp, chooses how many decimal places to expose for value, result, and value_lx, defaulting to ten and capped at fifteen so JSON goldens stay stable. Pair the free browser run on this page with the priced API when you need the identical mathematical result inside an automated pipeline without re-implementing photometric tables yourself.
Where illuminance conversion fits in design, photography, and software
On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split — free interactive exploration and a priced, identical API — matches the rest of the KIT tier-A catalog and lets you move from a classroom demo to an automated pipeline without changing the mathematical result.
Integration use cases
Homework and CI fixtures
Generate reproducible illuminance conversions for worksheets, tutoring software, and unit tests that assert fixed SI photometric factors.
Technical questions
Which illuminance units are supported?
Lux (lx), foot-candles (fc), phot (ph), and lumens per square meter (lm_m2), including common aliases such as lux, foot-candle, phot, and lm/m2.
How are conversion factors defined?
All conversions bridge through lux using fixed definitions: 1 lx = 1 lm/m², 1 lm_m2 = 1 lx, 1 fc = 10.763910416709722 lx (1 lm/ft² with the international foot), and 1 ph = 10,000 lx (1 lm/cm²).
Is lux the same as lumens per square meter?
Yes. By SI definition lux is one lumen per square meter, so converting between lx and lm_m2 is an identity. This tool still accepts both labels so clients can keep the unit name their domain prefers.