Parts per million (ppm) = (part ÷ total) × 1,000,000
ppm = (mass of solute ÷ mass of solution) × 1,000,000
ppm = (volume of solute ÷ volume of solution) × 1,000,000
ppm = (number of particles of interest ÷ total number of particles) × 1,000,000
Convert grams to milligrams when using mass-based ppm
1 ppm = 1 mg per kg
1 ppm = 1 mg per L in water-like solutions
Rearrange the formula to find the part: part = ppm × total ÷ 1,000,000
Rearrange the formula to find the total: total = part × 1,000,000 ÷ ppm
Example: 5 mg in 2,000,000 mg = 2.5 ppm
Example: 3 mg in 3 L of water = 1 ppm
Example: 0.0002 g in 1 kg = 0.2 ppm