Conversion Equation

Where 'd' is the distance from the light source in meters.

In case, If you would like to use feet instead of meters, then convert sq. meter to sq. feet. 

ie; 1 sq. mt. = 10.76391 sq. ft.

Candela

Candela (cd) is the SI unit of Luminous Intensity. It indicates the strength of light emission and is defined as the luminous power per unit solid angle emitted by a light source in a particular direction.

Luminous Flux / Luminous Power is the amount of light energy radiated from a source in all directions per second and is denoted as F.

Unit Solid Angle means the solid angle of a sphere subtended by a portion of the surface whose area is equal to the square of the sphere's radius.

Luminous Intensity (Iv) of a light source is the emitted luminous power or luminous flux per unit solid angle.

Lux

Lux (lx) is the SI unit of illumination. It indicates the illumination intensity of an area.

One Lux is equal to One Lumen per square meter.

illuminance (Ev) is the amount of luminous flux per unit area.