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ppm / Percent Converter

Convert concentrations between ppm, ppb and percent.

How it is calculated

The tool first converts your number to a plain fraction, then expresses that fraction in the other scales: fraction = value × factor, with factors ppm = 10-6, ppb = 10-9, percent = 10-2 and fraction = 1. The outputs are percent = fraction × 100, ppm = fraction × 106 and ppb = fraction × 109.

Choose the unit of the number you typed from the unit selector. Negative values are rejected and give no result, and zero is accepted. Percent is shown with six decimals, ppm with four and ppb with two. The conversion is purely numeric: it does not know whether your ppm is by mass, by volume or by mole, and that distinction is up to you.

Worked example

Convert 350 ppm.

Step 1: fraction = 350 × 10-6 = 0.00035. Step 2: percent = 0.00035 × 100 = 0.035000 %. Step 3: ppm = 0.00035 × 1,000,000 = 350.0000 ppm. Step 4: ppb = 0.00035 × 1,000,000,000 = 350,000.00 ppb.

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Common mistakes

  • Leaving the unit on ppm when the number is a percentage. Entering 0.0035 as ppm gives a result 10,000 times too small compared with entering it as percent.
  • Confusing ppm and ppb, which differ by a factor of 1,000. 350 ppb is only 0.35 ppm.
  • Moving the decimal by the wrong number of places between percent and ppm. One percent is 10,000 ppm, not 1,000 or 100,000.
  • Mixing mass-based and volume-based ppm. The tool treats the number as a pure ratio, so a gas concentration by volume is not the same as a water concentration by mass.

About this calculator

This converter moves a concentration value between four equivalent scales: percent (parts per hundred), ppm (parts per million), ppb (parts per billion), and plain decimal fraction — using the fixed relationships 1% = 10,000 ppm = 10,000,000 ppb = 0.01 as a fraction. In dilute aqueous solutions, 1 ppm is commonly treated as 1 mg per liter (since 1 L of water weighs almost exactly 1 kg).

Environmental scientists and lab technicians use ppm and ppb constantly for regulatory reporting — drinking-water contaminant limits, air-quality pollutant levels, and pesticide residue standards are all published in these units — while chemists, toxicologists, and agricultural engineers convert between them and percent when moving from lab-scale results to field-application concentrations like fertilizer or chemical dosing rates.

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