PPM to mg/kg Calculator
Going the other way: 80 PPM in a solid sample is 80 mg/kg. Same number, different label — valid whenever the PPM is mass-based.
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PPM to mg/kg Calculator
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Going the other way: 80 PPM in a solid sample is 80 mg/kg. Same number, different label — valid whenever the PPM is mass-based.
How to use this calculator
- Enter the PPM value.
- Confirm it is mass-based.
- That number is your mg/kg.
The formula
By definition, 1 mass-based PPM = 1 mg/kg.
What the units mean
PPM (parts per million) — one part of solute per million parts of the total mixture. The workhorse unit for trace concentrations in water, air, and food.
mg/kg — milligrams per kilogram, a mass-basis concentration. Numerically identical to PPM on a mass basis; the unit soil and food laboratories report in.
Worked example
A fertilizer contains 200 PPM zinc (mass) → 200 mg/kg for the label.
Quick reference
| PPM | mg/kg |
|---|---|
| 5 | 5 |
| 25 | 25 |
| 80 | 80 |
| 200 | 200 |
Same number, mass basis required.
Where you will actually use this
Lets you quote PPM findings in the mg/kg units that soil and food regulations use.
- Fertilizer labeling
- Soil reports
- Food compliance
- Waste classification
Mistakes that give wrong answers
- Using it for volume-based PPM
- Forgetting to state the basis
Key takeaways
- Formula: mg/kg = PPM (mass basis, numerically identical)
- Remember: Same number, mass basis required.
- Watch out for: Using it for volume-based PPM
- Next step: run your own numbers in the calculator above, then verify with a measurement — calculated values are only as good as the inputs.
Frequently asked questions
How do you convert PPM to mg/kg?
Use the same number — they are identical on a mass basis.
What is 75 PPM in mg/kg?
75 mg/kg.