Illuminance Converter

Convert any illuminance unit to another with this free illuminance converter. It supports 6 units including lux, millilux, kilolux, foot-candles, phot, nox. Pick a conversion below for a dedicated calculator, formula, and reference table. For example, 1 lx = 1000 mlx.

About these units

Lux (lx)

Definition: The lux (lx) is the SI unit of illuminance, equal to one lumen per square meter — a measure of how much light falls on a surface.
History: It was adopted as an SI unit in 1960, derived from the lumen and the meter.
Current use: Lux is used in lighting design, photography, agriculture (grow-light intensity), and workplace health and safety standards.

Millilux (mlx)

Definition: A millilux (mlx) is one thousandth of a lux, used for very low-light measurement.
History: It is a metric sub-multiple of the lux.
Current use: Millilux values describe moonlit or deeply shaded environments in scientific photometry.

Kilolux (klx)

Definition: A kilolux (klx) is 1,000 lux, representing bright indoor or outdoor lighting conditions.
History: It is a metric multiple of the lux used when values become large.
Current use: Direct sunlight reaches 100–130 klx; kilolux is used in horticultural and sports-facility lighting specs.

Foot-candle (fc)

Definition: A foot-candle (fc) is the illuminance produced by one lumen per square foot, equal to about 10.764 lux.
History: It originated in the era before the metric system and takes its name from the illuminance one foot from a standard candle.
Current use: Foot-candles remain the standard lighting unit in the United States for architectural and stage-lighting specifications.

Phot (ph)

Definition: A phot (ph) is a CGS unit of illuminance equal to 10,000 lux, or one lumen per square centimeter.
History: It was part of the CGS system, predating the SI, and is now largely obsolete.
Current use: The phot is rarely used today, appearing only in older technical literature.

Nox (nx)

Definition: A nox (nx) is a non-SI unit of illuminance equal to one millilux (0.001 lux), intended for very dim conditions.
History: It was proposed in the early 20th century for measuring nighttime light levels but was never officially standardised.
Current use: Nox is largely historical; modern low-light measurements use millilux or microlux instead.

Frequently asked questions

What illuminance units can I convert?

This illuminance converter supports 6 units: lux, millilux, kilolux, foot-candles, phot, nox. Select any pair below to open a dedicated converter with a formula and conversion table.

How accurate is the illuminance converter?

Conversions use exact definitional factors, so results are accurate to the precision you need for science, engineering, and everyday use. Values are rounded only for display.

Is the illuminance converter free?

Yes. Every illuminance conversion is completely free, needs no sign-up, and runs entirely in your browser — your inputs never leave your device.

Free, private, and instant — every conversion runs in your browser.

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