Why people use permille
Permille is useful where values are small but still meaningful: salinity, slope grades, rates, quality error percentages, and cost-per-thousand metrics.
Guide
What Is Permille?
Permille is a ratio format where the whole is 1,000. It uses the symbol ‰ and reads as "per thousand". The word "mille" comes from latin and means thousand.
Interpretation rule
Read any permille value as "this many out of 1,000." For example, 35‰ means 35 in every 1,000, equivalent to 3.5%.