PPM Calculator
Convert parts per million to milligrams per liter, percent, parts per billion and mg/kg — or calculate ppm from a mass in a mass or volume.
Parts per million in every unit a lab or a water report uses.
How the ppm calculator works
A part per million is one part in a million: 1 mg in 1 kg, or, for dilute aqueous solutions where a liter weighs a kilogram, 1 mg in 1 L. So ppm ≈ mg/L for water, 10,000 ppm is 1%, and 1 ppm is 1,000 ppb. Enter a value in any of the units and the calculator gives the others; in Detailed mode compute ppm from a solute mass in a sample mass.
Formula: ppm = mg/kg = (for water) mg/L · % = ppm ÷ 10,000 · ppb = ppm × 1,000
Worked examples
| Inputs | Parts per million | Note |
|---|---|---|
| 250 ppm | 250 ppm | 0.025%, 250 mg/L |
| 1.5% as ppm | 15,000 ppm | 15,000 ppm |
| 80 ppb | 0.08 ppm | 0.08 ppm |
| 12 mg of lead in 2 kg of soil | 0 ppm | Detailed: 6 ppm |
FAQFrequently asked questions
Is ppm the same as mg/L?
For dilute solutions in water, effectively yes — a liter of water weighs a kilogram. For dense liquids or gases it is not: ppm in air is by volume.
How many ppm is 1%?
10,000. And 1 ppm is 0.0001%.
What is ppm for a gas?
Usually parts per million by volume (ppmv): 400 ppm CO₂ means 400 molecules in every million of air.
How do I calculate ppm from a measurement?
Mass of the component in mg divided by the sample mass in kg (or volume in liters for water). 12 mg in 2 kg is 6 ppm.
Where these figures come from
- IUPAC — Standard atomic weights (2021 conventional values) — the molar-mass table
- NIST — CODATA 2018 fundamental physical constants — Avogadro constant, gas constant, speed of light
- NIST Chemistry WebBook — thermochemical data
- National Institute of Standards and Technology — the US measurement and reference-data authority
Last checked: September 2026. Atomic masses are the IUPAC conventional values; constants are CODATA 2018; equations are the standard textbook forms.