Understanding Parts Per Million (PPM)
Parts per million is a unit of measurement used to express very dilute concentrations. One ppm is equivalent to one part out of one million parts, or 0.0001%.
Formula
PPM = (Parts / Total) x 1,000,000
Common Uses
- Water quality testing
- Air pollution levels
- Chemical concentrations
- Food additives
- Soil contaminants
- Gas mixtures
Examples
Example 1: 5mg of chlorine in 1kg of water
PPM = (5 / 1,000,000) x 1,000,000 = 5 ppm
Example 2: 10 defects in 2 million products
PPM = (10 / 2,000,000) x 1,000,000 = 5 ppm
Related Units
- PPB (parts per billion) = PPM / 1,000
- PPT (parts per trillion) = PPM / 1,000,000
- Percentage = PPM / 10,000
Context Matters
What's considered high or low varies by substance. For example, 5 ppm of carbon monoxide in air is dangerous, but 5 ppm of fluoride in water is beneficial.
Conversion Quick Reference
1 ppm = 0.0001% = 1 mg/L (in water) = 1 mg/kg
Quick Tips
- Double-check your inputs for accurate results
- Use parentheses to clarify order of operations
- Results are rounded — consider significant figures
Frequently Asked Questions
Parts per million - one part in a million parts.
Divide parts by total and multiply by 1,000,000.
1 ppm = 0.0001%
Both - it's used for any mixture or concentration.
Multiply percentage by 10,000.
PPB (parts per billion) is 1,000 times smaller than PPM.