Convert Per cent to Parts per million
1 per cent is 10,000 ppm. One per cent is exactly 10000 parts per million.
One per cent is 10000 parts per million. To convert per cent to parts per million, multiply by 10000; to go the other way, divide by 10000 or multiply by 1.0000 × 10^-4. The factor is exact rather than rounded: it follows from NIST SP 811 §7.10.3. Parts per hundred.
Factor checked against the defining standard · How we check
- Per cent × 10000
1 * 1000010,000 ppm
1 per cent in every concentration unit
| Unit | Value | Exact factor |
|---|---|---|
| per cent (as entered) | 1 % | — |
| per mille | 10 ‰ | × 10 |
| parts per million | 10,000 ppm | × 10,000 |
| parts per billion | 10,000,000 ppb | × 10,000,000 |
| parts per trillion | 10,000,000,000 ppt | × 10,000,000,000 |
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 per cent to parts per million? The converter and the working
- 1.Take the measurement in per cent.
- 2.Multiply by 10000 — that is how many parts per million fit in one per cent.
- 3.To go back the other way, divide by 10000, or multiply by 1.0000 × 10^-4.
Worked example: 25 per cent to parts per million
- Formula
- % × 10000 = ppm
- Arithmetic
- 25 × 10000 = 250,000 ppm
- Answer
- 25 % = 250,000 ppm
The factor is exact, so this figure is exact too — only the display is rounded.
Per cent to parts per million conversion table
| Per cent | Parts per million |
|---|---|
| 1 % | 10,000 ppm |
| 2 % | 20,000 ppm |
| 3 % | 30,000 ppm |
| 4 % | 40,000 ppm |
| 5 % | 50,000 ppm |
| 6 % | 60,000 ppm |
| 7 % | 70,000 ppm |
| 8 % | 80,000 ppm |
| 9 % | 90,000 ppm |
| 10 % | 100,000 ppm |
| 12 % | 120,000 ppm |
| 15 % | 150,000 ppm |
| 20 % | 200,000 ppm |
| 25 % | 250,000 ppm |
| 50 % | 500,000 ppm |
| 100 % | 1,000,000 ppm |
| 200 % | 2,000,000 ppm |
| 300 % | 3,000,000 ppm |
| 500 % | 5,000,000 ppm |
| 1000 % | 10,000,000 ppm |
| 2000 % | 20,000,000 ppm |
| 5000 % | 50,000,000 ppm |
| 10000 % | 100,000,000 ppm |
1% is 10,000 ppm, and the factor catches people out in both directions
Per cent is parts per hundred and ppm is parts per million, so the step between them is 10,000 rather than 1,000 — one decimal place further than the eye expects. In water, 1 ppm is 1 milligram per liter, because a liter of water weighs a kilogram; that identity is why laboratory results and legal limits move between mg/L and ppm without conversion, and why 0.05% of chlorine is 500 ppm.
NIST Special Publication 811 — Guide for the Use of the International System of Units
What is a per cent?
Parts per hundred. One per cent is 10,000 ppm, which is the conversion people reach for when a water report and a lab result are in different 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.
How many parts per million are in a per cent?
One per cent is 10000 parts per million, exactly. Going the other way, one part per million is 1.0000 × 10^-4 per cent. 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 per cent.
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 per cent?
- 10000. 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 per cent?
- Divide by 10000, or multiply by 1.0000 × 10^-4 — they are the same operation.
Other concentration conversions
Parts per million to per cent — the same conversion the other way.