What is Log Reduction?

“Log reduction” is a mathematical term (as is “log increase”) used to show the relative number of live microbes eliminated from a surface by disinfecting or cleaning.

 

For example, a “5-log reduction” means lowering the number of microorganisms by 100,000-fold, that is, if a surface has 100,000 pathogenic microbes on it, a 5-log reduction would reduce the number of microorganisms to one.

 

Log Reductions

  • 1 log reduction means the number of germs is 10 times smaller
  • 2 log reduction means the number of germs is 100 times smaller
  • 3 log reduction means the number of germs is 1000 times smaller
  • 4 log reduction means the number of germs is 10,000 times smaller
  • 5 log reduction means the number of germs is 100,000 times smaller
  • 6 log reduction means the number of germs is 1,000,000 times smaller
  • 7 log reduction means the number of germs is 10,000,000 times smaller