Convert Parts per trillion to Parts per billion
1 part per trillion is 0.001 ppb. One part per trillion is exactly 0.001 parts per billion.
One part per trillion is 0.001 parts per billion. To convert parts per trillion to parts per billion, 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 million million.
Factor checked against the defining standard · How we check
- Parts per trillion × 0.001
1 * 0.0010.001 ppb
1 part per trillion in every concentration unit
| Unit | Value | Exact factor |
|---|---|---|
| per cent | 0.0000000001 % | × 0.0000000001 |
| per mille | 0.000000001 ‰ | × 0.000000001 |
| parts per million | 0.000001 ppm | × 0.000001 |
| parts per billion | 0.001 ppb | × 0.001 |
| parts per trillion (as entered) | 1 ppt | — |
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 trillion to parts per billion? The converter and the working
- 1.Take the measurement in parts per trillion.
- 2.Multiply by 0.001 — that is how many parts per billion fit in one part per trillion.
- 3.To go back the other way, divide by 0.001, or multiply by 1000.
Worked example: 25 parts per trillion to parts per billion
- Formula
- ppt × 0.001 = ppb
- Arithmetic
- 25 × 0.001 = 0.03 ppb
- Answer
- 25 ppt = 0.03 ppb
The factor is exact, so this figure is exact too — only the display is rounded.
Parts per trillion to parts per billion conversion table
| Parts per trillion | Parts per billion |
|---|---|
| 1 ppt | 0.001 ppb |
| 2 ppt | 0.002 ppb |
| 3 ppt | 0.003 ppb |
| 4 ppt | 0.004 ppb |
| 5 ppt | 0.01 ppb |
| 6 ppt | 0.01 ppb |
| 7 ppt | 0.01 ppb |
| 8 ppt | 0.01 ppb |
| 9 ppt | 0.01 ppb |
| 10 ppt | 0.01 ppb |
| 12 ppt | 0.01 ppb |
| 15 ppt | 0.02 ppb |
| 20 ppt | 0.02 ppb |
| 25 ppt | 0.03 ppb |
| 50 ppt | 0.05 ppb |
| 100 ppt | 0.1 ppb |
| 200 ppt | 0.2 ppb |
| 300 ppt | 0.3 ppb |
| 500 ppt | 0.5 ppb |
| 1000 ppt | 1 ppb |
| 2000 ppt | 2 ppb |
| 5000 ppt | 5 ppb |
| 10000 ppt | 10 ppb |
What is a part per trillion?
One in a million million. PFAS limits are set here — the EPA’s 2024 drinking-water rule is 4 ppt, which is four drops in a thousand Olympic pools.
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 trillion?
One part per trillion is 0.001 parts per billion, exactly. Going the other way, one part per billion is 1000 parts per trillion. 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 trillion.
Source: NIST SP 811 §7.10.3 — why ppm, ppb and ppt should be avoided and what they mean
Cite this page
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- Chicago
- Rule Calculator. "Convert Parts per trillion to parts per billion." Rule Calculator. Last reviewed August 16, 2026. https://rulecalculators.com/convert/ppt-to-ppb.
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Questions people actually ask
- How many parts per billion are in a part per trillion?
- 0.001. 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 trillion?
- Divide by 0.001, or multiply by 1000 — they are the same operation.
Other concentration conversions
Parts per billion to parts per trillion — the same conversion the other way.