Pure Live Seed (often referred to as PLS) refers to the percentage of live, viable seed in a bulk amount of seed. This percentage of seed is what is capable of developing into seedlings. PLS provides a standard of comparing the quality of lots of the same species that have different germination and purity. PLS is calculated by multiplying the percent of total germination and the percent of pure seed of a lot.
Example: 98% purity and 90% germination
98 x 90/100=88.2%
Only 88.2 percent of that lot of seed is capable of growing. If you have a 50-pound bulk bag of seed that would give you 44.1 pounds of live seed.