Online Tool Store
Luminosity Converter
Convert light output and illuminance between lumens, candela, lux, and foot-candles. Runs entirely in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Lumen ⇄ candela and lux ⇄ foot-candle conversions are exact; lumen ⇄ lux conversion assumes a 1 steradian solid angle (a simplification — real conversion depends on beam angle and distance).
How it works
- Enter a value and choose its unit.
- See the equivalent value in lumens, candela, lux, and foot-candles.
The formulas
Candela = lumens ÷ 4π (uniform sphere emission)
Lux ≈ lumens (1 steradian simplification)
Foot-candle = lux ÷ 10.7639 (exact)
FAQ
What is the difference between lumens and lux?
Lumens measure the total light output from a source, regardless of direction. Lux measures how much of that light actually lands on a surface (lumens per square meter) — the same bulb produces fewer lux the farther away or more spread out the light is.
Why is the lumen-to-lux conversion a simplification?
A precise conversion needs the beam angle and distance to the surface (lux = lumens ÷ area, and area depends on both) — this tool assumes a 1 steradian solid angle as a reasonable ballpark, clearly noted, rather than pretending to a precision the inputs don't support.
Is the candela conversion exact?
Yes, assuming even light output over a full sphere — candela = lumens ÷ 4π. This is the standard relationship for an isotropic (uniform in all directions) light source.
Is my data uploaded anywhere?
No — every calculation happens locally in your browser. Nothing is sent to a server.
How we compare
| Feature | Online Tool Store | Manual formula lookup | Lighting design software |
|---|---|---|---|
| All four units at once | ✓ | Convert one pair at a time | ✓ |
| No install | ✓ | ✓ | Requires dedicated software |
For a quick ballpark when comparing bulb specs or camera light meter readings, this beats looking up conversion factors by hand.