Convert Parts per million to Per mille
1 part per million is 0.001 ‰. One part per million is exactly 0.001 per mille.
One part per million is 0.001 per mille. To convert parts per million to per mille, 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.
Factor checked against the defining standard · How we check
- Parts per million × 0.001
1 * 0.0010.001 ‰
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 per mille? The converter and the working
- 1.Take the measurement in parts per million.
- 2.Multiply by 0.001 — that is how many per mille fit in one part per million.
- 3.To go back the other way, divide by 0.001, or multiply by 1000.
Worked example: 25 parts per million to per mille
- Formula
- ppm × 0.001 = ‰
- Arithmetic
- 25 × 0.001 = 0.03 ‰
- Answer
- 25 ppm = 0.03 ‰
The factor is exact, so this figure is exact too — only the display is rounded.
Parts per million to per mille conversion table
| Parts per million | Per mille |
|---|---|
| 1 ppm | 0.001 ‰ |
| 2 ppm | 0.002 ‰ |
| 3 ppm | 0.003 ‰ |
| 4 ppm | 0.004 ‰ |
| 5 ppm | 0.01 ‰ |
| 6 ppm | 0.01 ‰ |
| 7 ppm | 0.01 ‰ |
| 8 ppm | 0.01 ‰ |
| 9 ppm | 0.01 ‰ |
| 10 ppm | 0.01 ‰ |
| 12 ppm | 0.01 ‰ |
| 15 ppm | 0.02 ‰ |
| 20 ppm | 0.02 ‰ |
| 25 ppm | 0.03 ‰ |
| 50 ppm | 0.05 ‰ |
| 100 ppm | 0.1 ‰ |
| 200 ppm | 0.2 ‰ |
| 300 ppm | 0.3 ‰ |
| 500 ppm | 0.5 ‰ |
| 1000 ppm | 1 ‰ |
| 2000 ppm | 2 ‰ |
| 5000 ppm | 5 ‰ |
| 10000 ppm | 10 ‰ |
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 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 million?
One part per million is 0.001 per mille, exactly. Going the other way, one per mille is 1000 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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- Rule Calculator. (2026). Convert Parts per million to per mille. Rule Calculator. https://rulecalculators.com/convert/ppm-to-permille
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- Chicago
- Rule Calculator. "Convert Parts per million to per mille." Rule Calculator. Last reviewed August 16, 2026. https://rulecalculators.com/convert/ppm-to-permille.
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Questions people actually ask
- How many per mille are in a part per million?
- 0.001. 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 million?
- Divide by 0.001, or multiply by 1000 — they are the same operation.
Other concentration conversions
Per mille to parts per million — the same conversion the other way.