PPM to mg/L Converter — Parts Per Million to Milligrams per Litre
Convert a mass-based ppm concentration to mg/L (milligrams per litre) and related units. For dilute aqueous solutions 1 ppm = 1 mg/L exactly; for other liquids enter the solution density to apply the correct conversion factor.
ppm
g/mL
mg/L = ppm × density (g/mL); equals ppm exactly for water at standard conditions
- 1
Input concentration
5 mg/kg = 5 - 2
Apply density correction
5 × 1 g/mL = 5mg/L = ppm × density; equals ppm exactly when density = 1 g/mL (pure water).
How does this calculator work?
mg/L = ppm × density. For water (density = 1 g/mL), 1 ppm = 1 mg/L exactly. For other liquids, enter the actual density — seawater at 1.025 g/mL gives 1 ppm = 1.025 mg/L. Also converts to μg/L (ppb) and ng/L (ppt).
Formula
How this is calculated
Parts per million (ppm) expresses a mass fraction: one milligram of solute per kilogram of solution (mg/kg). Milligrams per litre (mg/L) is a mass-per-volume concentration. To convert between them you need the solution density: mg/L = ppm × ρ, where ρ is in g/mL (equivalently kg/L).
For dilute aqueous solutions — drinking water, environmental samples, most food-safety contexts — the density is so close to 1.000 g/mL that ppm and mg/L are numerically identical. This is the source of the common shorthand "1 ppm ≈ 1 mg/L in water", which holds to better than 0.1 % for concentrations below about 10,000 ppm.
For denser liquids (salt water, sugar solutions, acids, solvents), the density correction is significant. For example, seawater at 35 ‰ salinity has a density of approximately 1.025 g/mL, so 10 ppm in seawater equals 10.25 mg/L, not 10 mg/L. Enter the actual solution density for accurate results.
Frequently asked questions
Only for dilute aqueous solutions where the density is effectively 1 g/mL. For water at 4 °C the equality is exact; at 20 °C it is accurate to 0.02 %. For any other solvent or for concentrated solutions, use the actual density: mg/L = ppm × ρ.
For most practical purposes, 1.000 g/mL. The density of tap water ranges from about 0.998 g/mL at 20 °C to 0.999 g/mL at 10 °C — the difference from 1.000 is negligible for ppm-to-mg/L conversions.
Divide by the density: ppm = mg/L / ρ. For water (ρ = 1), ppm = mg/L. The converter on this page shows ppm → mg/L; reverse the formula for the other direction.
Also known as
TG we-Calculate Editorial Team. (2026). PPM to mg/L Converter — Parts Per Million to Milligrams per Litre [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/ppm-to-mgl-converter
TG we-Calculate Editorial Team. "PPM to mg/L Converter — Parts Per Million to Milligrams per Litre." TG we-Calculate. 2026. https://we-calculate.com/calculator/ppm-to-mgl-converter.
TG we-Calculate Editorial Team, "PPM to mg/L Converter — Parts Per Million to Milligrams per Litre," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/ppm-to-mgl-converter
@misc{wecalculate_ppm_to_mgl_converter, title = {PPM to mg/L Converter — Parts Per Million to Milligrams per Litre}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/ppm-to-mgl-converter}}, year = {2026}, note = {TG we-Calculate} }
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