The Parts Per Million (PPM) Calculator computes the concentration of a substance in a mixture expressed as parts per million. Users enter the mass of solute, the mass of solution, and select the units (either mg/kg or g/g × 10⁶). The calculator then divides the solute mass by the solution mass, applying the appropriate factor for the selected units, and outputs the PPM along with the substitution formula. This tool is useful for environmental chemistry, water analysis, and laboratory measurements requiring very low concentration calculations.