PPM Calculator
Compute parts per million from a part and a whole measured in the same unit. Enter both values to get ppm, along with the matching percent and decimal fraction.
Example: with Part 5 · Whole (same unit) 10000 → Parts per million: 500 ppm.
- As percent and fraction0.05% (0.0005 as a fraction)
- Formulappm = (part ÷ whole) × 1,000,000
Computed by the calculator below using its default values. Change any input to see your own numbers.
Parts per million counts how many units of a part sit in a million units of the whole: ppm = (part ÷ whole) × 1,000,000. Both values must share the same unit.
What parts per million means
Parts per million is a ratio scaled to a million. It answers how many units of something appear in every million units of a mixture. The math is a fraction times a million: divide the part by the whole, then multiply by 1,000,000. Five units in ten thousand is 500 ppm.
Because it is a pure ratio, ppm only works when the part and the whole share a unit — milligrams over milligrams, liters over liters, or counts over counts. ppm is a natural fit for tiny concentrations where percent gets clumsy: 0.05% reads more clearly as 500 ppm. The tool also shows the percent and the plain decimal fraction so you can move between all three.
How it’s calculated
ppm = (part ÷ whole) × 1,000,000. Percent = ppm ÷ 10,000; the decimal fraction = ppm ÷ 1,000,000. Part and whole must be in the same unit for the ratio to be dimensionless. Results round to 4 decimal places.
Treats ppm as a simple ratio by mass, volume, or count. For mass-in-volume concentrations like mg/L, density also matters — use the ppm to mg/L tool.
ppm, percent, and fraction
| Fraction | Percent | ppm |
|---|---|---|
| 1 / 1,000,000 | 0.0001% | 1 ppm |
| 1 / 10,000 | 0.01% | 100 ppm |
| 1 / 2,000 | 0.05% | 500 ppm |
| 1 / 1,000 | 0.1% | 1,000 ppm |
| 1 / 100 | 1% | 10,000 ppm |
Computed with ppm = (part ÷ whole) × 1,000,000; part and whole share one unit.
Common mistakes
- Using different units for part and whole — both must match, such as mg with mg or L with L.
- Forgetting ppm is a ratio: 500 ppm is 0.05%, not 5%.
- Dividing whole by part instead of part by whole, which inverts the answer.
Frequently asked questions
What is the parts per million formula?
ppm = (part ÷ whole) × 1,000,000. Divide the smaller quantity by the total, then multiply by one million.
How do I convert ppm to percent?
Divide ppm by 10,000. So 500 ppm is 500 ÷ 10,000 = 0.05%.
What is 5 in 10,000 in ppm?
(5 ÷ 10,000) × 1,000,000 = 500 ppm, which is also 0.05%.
Do the part and whole need the same units?
Yes. ppm is a ratio, so both must use one unit. Mixing, say, grams and kilograms without converting gives a wrong answer by a factor of 1,000.