Concentration (ppm) Calculator

These are progressively smaller concentration units: ppm (parts per million = 10⁻⁶), ppb (parts per billion = 10⁻⁹), ppt (parts per trillion = 10⁻¹²). 1 ppm = 1,000 ppb = 1,000,000 ppt. As analytical techniques improve, lower and lower concentrations of contaminants can be detected.

Drinking water standards set maximum contaminant levels in ppm (mg/L): lead < 0.015 ppm, arsenic < 0.010 ppm, nitrate < 10 ppm, fluoride < 4 ppm. These limits are based on health risk assessments and are regularly reviewed as new research emerges.

Atmospheric CO₂ is measured in ppm by volume (ppmv) — the number of CO₂ molecules per million air molecules. Pre-industrial levels were about 280 ppmv. Current levels are approximately 420 ppmv (as of 2024), representing a 50% increase. Each ppm increase adds approximately 2.13 billion tonnes of carbon to the atmosphere.