Calculate
Formula and method
Mass or volume ppm = (part ÷ total) × 1,000,000 after matching units. For mg/L, mass ppm = entered mg/L ÷ entered solution density in kg/L.
Worked example
5 mg in 2 kg total sample is 2.5 ppm by mass. At 10 mg/L and density 0.8 kg/L, the mass-based result is 12.5 ppm.
Assumptions and limitations
The quantity basis matters. mg/L is numerically equal to mass ppm only at density 1 kg/L. This tool gives no exposure, toxicity, environmental-limit, or regulatory interpretation.
Frequently asked question
Is 1 mg/L always 1 ppm?
No. Converting mass per volume to a mass fraction requires the solution density.
Methodology source
NIST SP 330 Section 5. Reference, not endorsement.