Brightness measures the reflectance of a specific wavelength in the blue-light color spectrum, which is 457 nanometers. And it is typically expressed on a scale of 1 to 100, with 100 being the brightest. Paper that has been rated in the 90’s will reflect more light than paper in the 80’s, so it will appear brighter.
If you’re looking for printer paper you can use for producing large documents, be sure to browse through the broad selection we have at Engineer Supply.