PPM to Percent Converter (and Percent to PPM)

How it works

Percent = ppm ÷ 10,000 · ppm = percent × 10,000 · ppm = ppb ÷ 1,000 · Per mille (‰) = ppm ÷ 1,000 · Decimal fraction = ppm ÷ 1,000,000 · ppb = ppm × 1,000 · ppt = ppm × 1,000,000 · Amount of substance = fraction × sample mass

Percent, per mille, ppm, ppb and ppt all describe the same thing, a part of a whole, on different scales: parts per hundred, per thousand, per million, per billion and per trillion. Start from the decimal fraction and multiply by 100 for percent, 1,000 for per mille, 1,000,000 for ppm, 10⁹ for ppb or 10¹² for ppt. Because a million is 10,000 times a hundred, ppm divided by 10,000 gives percent and percent times 10,000 gives ppm. The converter also shows the concentration as mg/kg (the same number as ppm by mass), as a “1 part in N” ratio and, for water, as mg/L. That last equivalence holds only for dilute water solutions, because one liter of water has a mass of about one kilogram (one million milligrams). Seawater, brines, oils and solvents have other densities, so divide mg/L by the density in kg/L to get ppm by mass. Gas concentrations such as CO₂ in air are usually ppm by volume, which converts to percent the same way. Under More options you can enter the total mass of a sample to see how much of the substance it holds, for example the milligrams of chlorine in a liter of disinfectant.

Worked example

With the default 2,500 ppm: percent = 2,500 ÷ 10,000 = 0.25%, per mille = 2,500 ÷ 1,000 = 2.5 ‰, ppb = 2,500 × 1,000 = 2,500,000 ppb and the decimal fraction = 2,500 ÷ 1,000,000 = 0.0025. That is 1 part in 400. In a 1 kg sample (about 1 L of a dilute water solution) the substance amounts to 0.0025 × 1 kg = 2.5 g. Going the other way, 0.25% × 10,000 = 2,500 ppm.

Sources: Omni Calculator: PPM calculator (percent, per mille, ppm, ppb, ppt and worked examples) · NIST: Unit conversion and SI references

Frequently asked questions