ConverterHub

Nox to Lux Converter

Enter a value and pick the conversion direction.

How it is calculated

The conversion uses one fixed ratio: lux = nox × 0.001 and nox = lux × 1000, so a nox is the same as a millilux. The direction setting chooses which way the number is read: nox2lux treats your value as nox and returns lux, while lux2nox treats it as lux and returns nox. If no direction is given, nox to lux is used. Results are rounded to three decimals. Illuminance cannot be negative, so a negative value returns nothing. The tool also shows the rate and a reverse line that repeats the result, built from the rounded figure. It converts the unit only: it does not account for the type of light, the surface or the sensor.

Worked example

A camera data sheet lists a minimum illumination of 250 nox. Direction: nox to lux. Lux = 250 × 0.001 = 0.250 lux. The tool also writes the reverse line, 0.250 lux = 250.000 nox, and the rate 1 nox = 0.001 lux. Going the other way, 0.25 lux × 1000 gives 250.000 nox, so the two directions agree.

Try this example →

Common mistakes

  • Leaving the direction on the wrong setting. With nox to lux selected, a value that is already in lux is shrunk by 1000 again; check the unit printed after the result.
  • Dividing when you should multiply. Going from lux to nox makes the number 1000 times bigger, because nox is the smaller unit.
  • Expecting the nox to be a different measure of light from lux. It is only a millilux, the same quantity with a different scale, so no conversion factor beyond 1000 is needed.
  • Entering very small values and trusting the display. Results are rounded to three decimals, so 0.0004 nox shows as 0.000 lux; the reverse line then reads 0.000 nox, which is the rounded figure, not the real one.
  • Entering a negative number. Illuminance below zero does not exist, so no result is returned.

About this calculator

Nox is a niche photometric unit for extremely low illuminance, defined as one-thousandth of a lux (1 nox = 0.001 lux) — small enough to measure the faint light levels found under starlight or moonlight, well below what a standard lux meter can usefully resolve. This calculator converts values between nox and lux in either direction using that fixed 1000:1 ratio.

The unit is mostly encountered in night-vision equipment specifications and low-light imaging, where manufacturers rate a camera or image intensifier's minimum operating illuminance in nox precisely because the light levels involved (overcast starlight can be under 1 millilux, which is the same as 1 nox) are too dim to express conveniently in lux alone. Military and security-optics documentation is the most common place this conversion actually comes up.

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