PPM Concentration Calculator
Parts per million (ppm) is used to express the concentration of trace substances in solutions, air, or other mixtures. It equals the mass of the solute divided by the mass of the solution, multiplied by one million. For dilute aqueous solutions at room temperature, 1 ppm is approximately equal to 1 mg/L (1 microgram per milliliter) because the density of water is very close to 1 g/mL. Enter the mass of solute and the mass of the solution (both in the same units, or as indicated below) to find concentration in ppm, mg/L, and percent.
PPM formula
ppm = (mass of solute / mass of solution) * 1,000,000 ppm = mg solute / kg solution (since 1 kg = 1,000,000 mg) % = ppm / 10,000 mg/L = ppm (for dilute aqueous solutions, density approximately 1 g/mL)
To use consistent units: if solute is in mg and solution is in kg, ppm = mg/kg directly. If using grams: ppm = (g solute / g solution) * 1,000,000.
Regulatory context for ppm
- EPA drinking water maximum contaminant levels (MCLs) are set in mg/L (= ppm). For example, nitrate MCL is 10 ppm, lead action level is 0.015 ppm (15 ppb).
- OSHA permissible exposure limits (PELs) for airborne chemicals are often in ppm by volume.
- Food safety: FDA sets ppm tolerances for pesticide residues in food.
- PPB (parts per billion) = ppm / 1,000 = mg/L / 1,000 = microg/L.
- PPT (parts per trillion) = ppm / 1,000,000 = nanograms/L.
Frequently asked questions
What does ppm mean in chemistry?
Parts per million (ppm) is a unit of concentration meaning one part of solute per one million parts of solution by mass. For dilute aqueous solutions, 1 ppm = 1 mg/kg = 1 mg/L (since water density is approximately 1 kg/L).
How is ppm calculated?
PPM = (mass of solute / mass of solution) * 1,000,000. Both masses must be in the same units. For example, 5 mg of NaCl in 1 kg (1,000,000 mg) of water = 5/1,000,000 * 1,000,000 = 5 ppm.
When is ppm used?
PPM is used for very dilute solutions such as trace contaminants in water (EPA drinking water limits are often in ppm or ppb), environmental pollutants, trace metals in food, and industrial process chemistry.
What is the difference between ppm by mass and ppm by volume?
PPM by mass (mg/kg) is mass of solute per million grams of solution. PPM by volume (mL/L) is volume of solute per million mL of solution. For dilute aqueous solutions they are approximately equal because water density is approximately 1 g/mL.
How do I convert ppm to percent?
Percent = ppm / 10,000. So 5,000 ppm = 0.5%. Conversely, 1% = 10,000 ppm. PPM is useful for expressing very small concentrations where percent values would have many leading zeros.
Official sources
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.