Lux and nits are both measurements of illuminance or illumination. In other words, they are measures of the intensity of light. Analogous to force, the unit "lumens" measures how hard light is pushing off of a light source. When it's spread out over a specified flat surface, you get lumens per square centimeter, analogous to pressure. One lumen per one square centimeter is exactly 1 lux. Similarly, a nit measures light "force" per steradian - essentially, per a curved surface.
Determine the illuminance or illumination in nits, from given data or experimentation.
Multiply the nits value by π ("pi"): 3.14159. For example, 10 nits times π equals 31.4159.
The previous result is nits converted to lux. With the example numbers, 10 nits equals 31.4159 lux.