How it's calculated
mg/L = ppm × 1
ppm = parts per million by mass, mg/L = milligrams per litre. They are equal in dilute water because 1 L of water ≈ 1 kg.
Common values
| PPM | mg/L |
|---|---|
| 1 ppm | 1 mg/L |
| 10 ppm | 10 mg/L |
| 50 ppm | 50 mg/L |
| 100 ppm | 100 mg/L |
Common questions
Why is 1 ppm equal to 1 mg/L?
Because water weighs about 1 gram per milliliter, so a milligram in a liter is one part in a million by mass.
Does this hold for any liquid?
Only for dilute aqueous solutions near water density. For dense or concentrated liquids the equality breaks down.