What Is The BR Number On Light Bulbs?
Comparison of the sizes of BR and PAR floodlights.
The size or diameter of the light bulb is essentially what distinguishes a BR20, BR30, and BR40. The figure denotes divisions of an eighth of an inch. For instance, a BR30 has a diameter of 3.75 inches and is 30/8ths of an inch, or 30 divided by 8.