Convert Parts per billion to Parts per million
1 part per billion is 0.001 ppm. One part per billion is exactly 0.001 parts per million.
One part per billion is 0.001 parts per million. To convert parts per billion to parts per million, multiply by 0.001; to go the other way, divide by 0.001 or multiply by 1000. The factor is exact rather than rounded: it follows from NIST SP 811 §7.10.3. One in a thousand million, on the short scale.
Factor checked against the defining standard · How we check
- Parts per billion × 0.001
1 * 0.0010.001 ppm
1 part per billion in every concentration unit
| Unit | Value | Exact factor |
|---|---|---|
| per cent | 0.0000001 % | × 0.0000001 |
| per mille | 0.000001 ‰ | × 0.000001 |
| parts per million | 0.001 ppm | × 0.001 |
| parts per billion (as entered) | 1 ppb | — |
| parts per trillion | 1,000 ppt | × 1,000 |
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 billion to parts per million? The converter and the working
- 1.Take the measurement in parts per billion.
- 2.Multiply by 0.001 — that is how many parts per million fit in one part per billion.
- 3.To go back the other way, divide by 0.001, or multiply by 1000.
Worked example: 25 parts per billion to parts per million
- Formula
- ppb × 0.001 = ppm
- Arithmetic
- 25 × 0.001 = 0.03 ppm
- Answer
- 25 ppb = 0.03 ppm
The factor is exact, so this figure is exact too — only the display is rounded.
Parts per billion to parts per million conversion table
| Parts per billion | Parts per million |
|---|---|
| 1 ppb | 0.001 ppm |
| 2 ppb | 0.002 ppm |
| 3 ppb | 0.003 ppm |
| 4 ppb | 0.004 ppm |
| 5 ppb | 0.01 ppm |
| 6 ppb | 0.01 ppm |
| 7 ppb | 0.01 ppm |
| 8 ppb | 0.01 ppm |
| 9 ppb | 0.01 ppm |
| 10 ppb | 0.01 ppm |
| 12 ppb | 0.01 ppm |
| 15 ppb | 0.02 ppm |
| 20 ppb | 0.02 ppm |
| 25 ppb | 0.03 ppm |
| 50 ppb | 0.05 ppm |
| 100 ppb | 0.1 ppm |
| 200 ppb | 0.2 ppm |
| 300 ppb | 0.3 ppm |
| 500 ppb | 0.5 ppm |
| 1000 ppb | 1 ppm |
| 2000 ppb | 2 ppm |
| 5000 ppb | 5 ppm |
| 10000 ppb | 10 ppm |
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 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.
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.
How many parts per million are in a part per billion?
One part per billion is 0.001 parts per million, exactly. Going the other way, one part per million is 1000 parts per billion. 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 billion.
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 million are in a part per billion?
- 0.001. 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.
- How do I convert parts per million back to parts per billion?
- Divide by 0.001, or multiply by 1000 — they are the same operation.
Other concentration conversions
Parts per million to parts per billion — the same conversion the other way.