Illuminance Converter

Illuminance measures the total luminous flux incident on a surface per unit area. It is a fundamental quantity in lighting design, photography, horticulture, and architecture. Our Illuminance Converter provides instant, accurate conversions between four key units: lux (lx), foot-candle (fc), phot (ph), and nox. Lux, the SI unit, represents one lumen per square meter. Foot-candle, used mainly in North America, equals one lumen per square foot. Phot, an older CGS unit, equals 10,000 lux (one lumen per square centimeter). Nox, a lesser-known unit, is one millilux, often used in very low light contexts.

Whether you're sizing office lighting, calculating grow light intensity, or verifying cinematography requirements, this tool eliminates manual errors. The converter uses precise factors: 1 foot-candle = 10.76391 lux, 1 phot = 10000 lux, 1 nox = 0.001 lux. Simply enter any value, choose source and target units, and the converted result appears immediately. The swap button lets you reverse the conversion direction. All calculations happen in real time with JavaScript, ensuring privacy and speed—no data leaves your device.

We designed this illuminance converter for maximum usability. It works on any screen—desktop, tablet, or phone—with large touch targets and clear typography. The tool also helps students grasp photometric concepts: by experimenting with values, you can see how the same illuminance is expressed in different unit systems. For example, 1 phot equals 929.0304 foot-candles, demonstrating the scale difference between metric and imperial illuminance standards.

Professionals in lighting often need to convert between lux and foot-candles when working with international standards. This tool also supports phot and nox for specialized applications: phot is occasionally used in very high illuminance settings (like bright sunlight), while nox appears in low-light engineering. Our converter covers all these bases. The interface is intentionally minimal—no distracting elements, only the conversion engine and essential information. We’ve also ensured the tool is fully accessible, with semantic HTML and proper labels for screen readers.

We continuously update our calculators based on user feedback. If you need additional illuminance units (such as lumens per square inch or watt‑related measures), please contact us via the navigation menu. The MultiCalculators team is committed to providing reliable, free online tools for everyday calculations. This illuminance converter is part of our suite of engineering and utility calculators. Use it as many times as needed, bookmark it, and share it with colleagues. No registration, no paywall—just honest, accurate conversion.