ppm Formula and ppm Calculator
The ppm Formula and ppm Calculator
Calculate ppm, the mass needed for a standard and ppm-to-molarity conversion, for AAS, ICP and water analysis.
What is ppm?
ppm (parts per million) means one part in a million parts of mixture. For dilute aqueous solutions the density is close to 1 g/mL, so 1 ppm = 1 mg/L = 1 µg/mL. It is used for very low concentrations such as heavy metals in water or AAS standards.
ppm formula
| Conversion | Formula |
|---|---|
| ppm to ppb | ppb = ppm × 1000 |
| ppm to percent | % = ppm ÷ 10,000 |
| ppm to molarity | M = ppm ÷ (Mr × 1000) |
| molarity to ppm | ppm = M × Mr × 1000 |
Worked examples
Example 1: calculating ppm
A 2 L water sample contains 5 mg of lead. What is the concentration?
- ppm = 5 mg ÷ 2 L = 2.5 mg/L
Answer: 2.5 ppm.
Example 2: a standard from a salt
Prepare 1 L of 100 ppm Cu from CuSO4·5H2O (249.68 g/mol; Cu 63.55).
- Cu needed = 100 mg
- salt = 100 mg × (249.68 ÷ 63.55)
Answer: weigh 392.9 mg of CuSO4·5H2O and make up to 1 L.
Example 3: diluting a standard
Make 100 mL of 10 ppm from a 1000 ppm stock.
- 1000 × V1 = 10 × 100
- V1 = 1 mL
Answer: pipette 1 mL of stock into a 100 mL volumetric flask and fill to the mark.
Example 4: ppm to molarity
What is the molarity of 58.44 ppm NaCl (58.44 g/mol)?
- M = 58.44 ÷ (58.44 × 1000) = 0.001 M
Answer: 1 mM.
Frequently asked questions
Is ppm the same as mg/L?
For dilute aqueous solutions, yes. Otherwise ppm by mass = mg/kg and must be corrected with density.
What is the difference between ppm and ppb?
1 ppm = 1000 ppb; ppb equals µg/L for dilute solutions.
How do I convert percent to ppm?
Multiply by 10,000: 0.5% equals 5000 ppm.
Does the dilution formula work with ppm?
Yes: ppm1 × V1 = ppm2 × V2.
Prepare solutions with analytical-grade reagents
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