Convert Parts per million to Parts per billion
1 part per million is 1,000 ppb. One part per million is exactly 1000 parts per billion.
One part per million is 1000 parts per billion. To convert parts per million to parts per billion, multiply by 1000; to go the other way, divide by 1000 or multiply by 0.001. The factor is exact rather than rounded: it follows from NIST SP 811 §7.10.3. One in a million.
Factor checked against the defining standard · How we check
- Parts per million × 1000
1 * 10001,000 ppb
1 part per million in every concentration unit
| Unit | Value | Exact factor |
|---|---|---|
| per cent | 0.0001 % | × 0.0001 |
| per mille | 0.001 ‰ | × 0.001 |
| parts per million (as entered) | 1 ppm | — |
| parts per billion | 1,000 ppb | × 1,000 |
| parts per trillion | 1,000,000 ppt | × 1,000,000 |
Factors are entered by hand from NIST SP 811 §7.10.3 rather than derived from a units library, so the ones that terminate are exact rather than rounded.
How do you convert parts per million to parts per billion? The converter and the working
- 1.Take the measurement in parts per million.
- 2.Multiply by 1000 — that is how many parts per billion fit in one part per million.
- 3.To go back the other way, divide by 1000, or multiply by 0.001.
Worked example: 25 parts per million to parts per billion
- Formula
- ppm × 1000 = ppb
- Arithmetic
- 25 × 1000 = 25,000 ppb
- Answer
- 25 ppm = 25,000 ppb
The factor is exact, so this figure is exact too — only the display is rounded.
Parts per million to parts per billion conversion table
| Parts per million | Parts per billion |
|---|---|
| 1 ppm | 1,000 ppb |
| 2 ppm | 2,000 ppb |
| 3 ppm | 3,000 ppb |
| 4 ppm | 4,000 ppb |
| 5 ppm | 5,000 ppb |
| 6 ppm | 6,000 ppb |
| 7 ppm | 7,000 ppb |
| 8 ppm | 8,000 ppb |
| 9 ppm | 9,000 ppb |
| 10 ppm | 10,000 ppb |
| 12 ppm | 12,000 ppb |
| 15 ppm | 15,000 ppb |
| 20 ppm | 20,000 ppb |
| 25 ppm | 25,000 ppb |
| 50 ppm | 50,000 ppb |
| 100 ppm | 100,000 ppb |
| 200 ppm | 200,000 ppb |
| 300 ppm | 300,000 ppb |
| 500 ppm | 500,000 ppb |
| 1000 ppm | 1,000,000 ppb |
| 2000 ppm | 2,000,000 ppb |
| 5000 ppm | 5,000,000 ppb |
| 10000 ppm | 10,000,000 ppb |
The billion in ppb is the American one, and that is a factor of a thousand
A part per billion means 10⁻⁹ on the short scale used in the US and, since 1974, in British government statistics. On the long scale still used across much of continental Europe a billion is 10¹², which makes ppb mean something a thousand times smaller. NIST asks for 10⁻⁹ or µg/kg to be written instead, precisely because the word is ambiguous and the numbers are limits people act on.
NIST Special Publication 811 — Guide for the Use of the International System of Units
What is a part per million?
One in a million. The working unit of drinking-water limits, CO₂ in air and dissolved solids — 1 ppm is 1 mg per liter of water, since a liter weighs a kilogram.
What is a part per billion?
One in a thousand million, on the short scale. The EPA states lead and arsenic limits in it, and the ambiguity of "billion" is exactly why NIST asks for 10⁻⁹ instead.
How many parts per billion are in a part per million?
One part per million is 1000 parts per billion, exactly. Going the other way, one part per billion is 0.001 parts per million. Both figures come from the same defined relation rather than from a measurement, which is why they are the same today as they were in 1959.
Every concentration unit here
The whole group — 5 units with their symbols and the size of each one in part per millions — is on the conversion index, along with every pair it makes. The table above already gives each of them relative to a part per million.
Source: NIST SP 811 §7.10.3 — why ppm, ppb and ppt should be avoided and what they mean
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Questions people actually ask
- How many parts per billion are in a part per million?
- 1000. One in a thousand million, on the short scale. The EPA states lead and arsenic limits in it, and the ambiguity of "billion" is exactly why NIST asks for 10⁻⁹ instead.
- How do I convert parts per billion back to parts per million?
- Divide by 1000, or multiply by 0.001 — they are the same operation.
Other concentration conversions
Parts per billion to parts per million — the same conversion the other way.