PPM to Percent Converter
Parts per million, percent, per mille and ppb, all from one number.
The conversion
These are all fractions of a whole with different denominators: percent is parts per hundred, per mille per thousand, ppm per million, ppb per billion. Each step is a factor of ten or a thousand: 1% = 10‰ = 10,000 ppm = 10,000,000 ppb. To go from ppm to percent, divide by 10,000.
Where ppm shows up
Water hardness and pollutant limits are quoted in ppm (1 ppm in water is 1 mg per liter). CO₂ in air passed 420 ppm, which is 0.042%. Blood alcohol limits like 0.5‰ are per mille. Trace contaminants and dosing errors live in ppb.
Per mille and the alcohol limit
The ‰ sign is per mille, parts per thousand. Most of Europe sets driving limits in per mille (0.2‰ in Norway, 0.5‰ in most of the EU) while the US writes the same quantity as a percent: 0.08% BAC equals 0.8‰.