Conversion method
Illuminance is luminous flux incident per area. Footcandle means lumen per square foot; lux is lumen per square meter.
fc = x × 0.09290304
10 lx = 0.92903 fc.
| lx | fc |
|---|---|
| 1 | 0.092903 |
| 5 | 0.464515 |
| 10 | 0.92903 |
| 25 | 2.322576 |
| 50 | 4.645152 |
| 100 | 9.290304 |
Unit definitions and sources
Illuminance is luminous flux incident per area. Footcandle means lumen per square foot; lux is lumen per square meter.
| Unit and system | Use | Definition | Relationship |
|---|---|---|---|
| Lux (lx); si | Common units | Lux: base (lx) = value × 1. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Footcandle (fc); si | Common units | Footcandle: base (lx) = value × 10.763910416709722. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Phot (ph); si | Specialist units | Phot: base (lx) = value × 10000.0. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Kilolux (klx); si | Specialist units | Kilolux: base (lx) = value × 1000. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Millilux (mlx); si | Specialist units | Millilux: base (lx) = value × 0.001. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Exalux (Elx); si | Specialist units | exalux: E denotes 10^18; the unit gives 1000000000000000000 lx. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Petalux (Plx); si | Specialist units | petalux: P denotes 10^15; the unit gives 1000000000000000 lx. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Teralux (Tlx); si | Specialist units | teralux: T denotes 10^12; the unit gives 1000000000000 lx. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Gigalux (Glx); si | Specialist units | gigalux: G denotes 10^9; the unit gives 1000000000 lx. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Megalux (Mlx); si | Specialist units | megalux: M denotes 10^6; the unit gives 1000000 lx. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Hectolux (hlx); si | Specialist units | hectolux: h denotes 10^2; the unit gives 100 lx. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Decalux (dalx); si | Specialist units | decalux: da denotes 10^1; the unit gives 10 lx. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Decilux (dlx); si | Specialist units | decilux: d denotes 10^-1; the unit gives 0.1 lx. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Centilux (clx); si | Specialist units | centilux: c denotes 10^-2; the unit gives 0.01 lx. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Microlux (µlx); si | Specialist units | microlux: µ denotes 10^-6; the unit gives 0.000001 lx. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Nanolux (nlx); si | Specialist units | nanolux: n denotes 10^-9; the unit gives 1e-9 lx. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Picolux (plx); si | Specialist units | picolux: p denotes 10^-12; the unit gives 1e-12 lx. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Femtolux (flx); si | Specialist units | femtolux: f denotes 10^-15; the unit gives 1e-15 lx. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Attolux (alx); si | Specialist units | attolux: a denotes 10^-18; the unit gives 1e-18 lx. Common use: Illuminance. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
Sources: NIST: SP 811 Appendix B.8: conversion factors; BIPM: SI prefixes
Precision of illuminance conversions
All 19 illuminance units convert through Lux (lx). 19 have an exact defined relationship to the base unit and 0 are conventional or measured values. Results and the tables on this page come from the same engine, so a table value can be checked against the converter directly.
Standard display shows up to six decimal places, switching to scientific notation for very large or small values. Calculation uses JavaScript binary floating point independently of display rounding, so extra digits are not a claim about measurement accuracy. Each unit lists its own source; a citation records where the definition comes from, not an independent review. See Conversion methodology for the review and correction process.