Convert Parts per trillion to Per mille
1 part per trillion is 1.00e-9 ‰. One part per trillion is exactly 1e-9 per mille.
One part per trillion is 1.0000 × 10^-9 per mille. To convert parts per trillion to per mille, multiply by 1.0000 × 10^-9; to go the other way, divide by 1.0000 × 10^-9 or multiply by 1000000000. The relation is exact but the figure is not: it is a rounding of a number that does not terminate, and 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 × 1.0000 × 10^-9
1 * 1e-90 ‰
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 per mille? The converter and the working
- 1.Take the measurement in parts per trillion.
- 2.Multiply by 1.0000 × 10^-9 — that is how many per mille fit in one part per trillion.
- 3.To go back the other way, divide by 1.0000 × 10^-9, or multiply by 1000000000.
Worked example: 25 parts per trillion to per mille
- Formula
- ppt × 1.0000 × 10^-9 = ‰
- Arithmetic
- 25 × 1.0000 × 10^-9 = 2.50e-8 ‰
- Answer
- 25 ppt = 2.50e-8 ‰
The factor is rounded for display; the figure above is computed from the full value.
Parts per trillion to per mille conversion table
| Parts per trillion | Per mille |
|---|---|
| 1 ppt | 1.00e-9 ‰ |
| 2 ppt | 2.00e-9 ‰ |
| 3 ppt | 3.00e-9 ‰ |
| 4 ppt | 4.00e-9 ‰ |
| 5 ppt | 5.00e-9 ‰ |
| 6 ppt | 6.00e-9 ‰ |
| 7 ppt | 7.00e-9 ‰ |
| 8 ppt | 8.00e-9 ‰ |
| 9 ppt | 9.00e-9 ‰ |
| 10 ppt | 1.00e-8 ‰ |
| 12 ppt | 1.20e-8 ‰ |
| 15 ppt | 1.50e-8 ‰ |
| 20 ppt | 2.00e-8 ‰ |
| 25 ppt | 2.50e-8 ‰ |
| 50 ppt | 5.00e-8 ‰ |
| 100 ppt | 1.00e-7 ‰ |
| 200 ppt | 2.00e-7 ‰ |
| 300 ppt | 3.00e-7 ‰ |
| 500 ppt | 5.00e-7 ‰ |
| 1000 ppt | 0.000001 ‰ |
| 2000 ppt | 0.000002 ‰ |
| 5000 ppt | 0.000005 ‰ |
| 10000 ppt | 0.00001 ‰ |
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 per mille?
Parts per thousand, written ‰. Used for blood alcohol in most of Europe, for salinity, and for slope in rail engineering.
How many per mille are in a part per trillion?
One part per trillion is 1.0000 × 10^-9 per mille. Going the other way, one per mille is 1000000000 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
- APA
- Rule Calculator. (2026). Convert Parts per trillion to per mille. Rule Calculator. https://rulecalculators.com/convert/ppt-to-permille
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- "Convert Parts per trillion to per mille." Rule Calculator, August 16, 2026, https://rulecalculators.com/convert/ppt-to-permille.
- Chicago
- Rule Calculator. "Convert Parts per trillion to per mille." Rule Calculator. Last reviewed August 16, 2026. https://rulecalculators.com/convert/ppt-to-permille.
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Questions people actually ask
- How many per mille are in a part per trillion?
- 1.0000 × 10^-9. Parts per thousand, written ‰. Used for blood alcohol in most of Europe, for salinity, and for slope in rail engineering.
- How do I convert per mille back to parts per trillion?
- Divide by 1.0000 × 10^-9, or multiply by 1000000000 — they are the same operation.
Other concentration conversions
Per mille to parts per trillion — the same conversion the other way.