Pharma Impurity PPM Calculator
ICH guidelines set impurity limits like "not more than 10 PPM" while chromatograms report area percent. 0.001% = 10 PPM — convert and compare against the limit.
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Pharma Impurity PPM Calculator
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ICH guidelines set impurity limits like "not more than 10 PPM" while chromatograms report area percent. 0.001% = 10 PPM — convert and compare against the limit.
How to use this calculator
- Enter impurity %.
- Convert to PPM.
- Compare with the specification limit.
The formula
% × 10,000 = PPM.
What the units mean
Percent — parts per hundred. The everyday unit for concentrations large enough to read as a percentage.
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.
Worked example
Impurity at 0.0008% → 8 PPM — under a 10 PPM limit.
Quick reference
| Impurity % | PPM |
|---|---|
| 0.0005% | 5 |
| 0.001% | 10 |
| 0.01% | 100 |
% × 10,000.
Where you will actually use this
A misplaced decimal in impurity math can fail a whole batch.
- QC release testing
- Method validation
- Stability studies
Mistakes that give wrong answers
- Area% vs w/w% confusion
- Wrong limit (check the current ICH Q3)
Key takeaways
- Formula: PPM = impurity % × 10,000
- Remember: % × 10,000.
- Watch out for: Area% vs w/w% confusion
- 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
What is the ICH impurity limit?
Varies by dose and impurity type — commonly 0.05–0.10% (500–1,000 PPM) for unspecified, lower for genotoxic.