Parts per million and parts per billion describe very small proportions, such as CO₂ in air (about 420 ppm) or lead in drinking water (U.S. action level 15 ppb). They are just fractions: 1 ppm is 0.0001% and 1% is 10,000 ppm.
How to use the PPM Calculator
- Pick the unit you are starting from in the From menu and type your value.
- Pick the unit you want in the To menu. The heading changes to match – for example “Parts per Million to Percent Converter”.
- The most common concentration units are shown below at the same time, so you can compare them at a glance.
- Type into any result to convert backwards, then use Copy results – the copied text starts with the heading for your chosen units.
Results update as you type. Everything is calculated in your browser.
How it works
Every concentration unit is defined by an exact factor relative to the part (the base unit). The calculator first turns the value you type into parts, then turns that into the unit you picked in the “To” menu and into each of the common units below it. This two-step method means any unit can be converted to any other – 6 units are available in each menu – and you can type into any field, including a result, to work in the other direction. Changing a unit menu keeps the quantity the same and just re-expresses it, and the page heading and copied results follow your choice.
How to convert concentration units
- Choose the unit you have in the From menu and type the value, for example 400 ppm.
- Choose the unit you want in the To menu, for example percent. The page heading changes to “Parts per Million to Percent Converter”.
- The calculator multiplies by the part factor of the “from” unit and divides by the factor of the “to” unit: 400 ppm × 1 × 10-6 ÷ 0.01 = 0.04 %.
1 part per million in common units
| Unit | Value |
|---|---|
| Percent (%) | 1 × 10-4 |
| Per mille (‰) | 0.001 |
| Parts per billion (ppb) | 1000 |
| Parts per trillion (ppt) | 1,000,000 |
| Parts (fraction) | 1 × 10-6 |
Parts per million conversion table
| Parts per million | % | ‰ | ppb | ppt |
|---|---|---|---|---|
| 1 | 1 × 10-4 | 0.001 | 1000 | 1,000,000 |
| 10 | 0.001 | 0.01 | 10,000 | 10,000,000 |
| 100 | 0.01 | 0.1 | 100,000 | 100,000,000 |
| 400 | 0.04 | 0.4 | 400,000 | 400,000,000 |
| 1,000 | 0.1 | 1 | 1,000,000 | 1 × 109 |
| 10,000 | 1 | 10 | 10,000,000 | 1 × 1010 |
What is a part per million?
Parts per million is a ratio of 1 in 1,000,000, used for trace concentrations in air and water.
What is a percent?
Percent means per hundred: 1% is 1/100.
Formula
1 ppm = 1 × 10^-4 %1 ppm = 0.001 ‰1 ppm = 1000 ppb1 ppm = 1,000,000 ppt1 ppm = 1 × 10^-6 fractionWorked example
Inputs — From: 400 ppm.
Results — To = 0.04 %; Per mille = 0.4 ‰; Parts per billion = 400,000 ppb; Parts per trillion = 400,000,000 ppt; Parts = 0.0004 fraction.
Frequently asked questions
How many ppm is 1%?
10,000 ppm.
Is ppm by mass or by volume?
Either; it must be stated. For dilute water solutions 1 ppm ≈ 1 mg/L.
What is ppt?
Usually parts per trillion (10⁻¹²), but some fields use it for parts per thousand, so check the context.
How do I change the units?
Pick any unit in the From and To menus. The value is converted in place, and the heading changes to show your conversion, for example “Parts per Million to Percent Converter”.
Can I type into any field?
Yes. Every field is editable, so you can start from whichever unit you have.
How many units can I convert between?
6 concentration units, from the everyday to the specialised.
Which units are exact?
All factors here are exact by definition except astronomical and similar reference values, which use internationally agreed constants.
What formula does the PPM Calculator use?
1 ppm = 1 × 10^-4 %.