How this calculator works
This tool defines ppm as mg solute per kg solution, not automatically mg/L. Multiply the mass fraction by solution density to obtain mass per volume, then divide by molar mass. For dilute water near density 1 kg/L the numerical mg/L and ppm values are close. Use solution density; solvent density is only a dilute-solution approximation.
Formula
c(mol/m3) = ppm x density(kg/m3) x 1000 / [10^6 x M(g/mol)]; replace 10^6 by 10^9 for ppb.
Worked example
100 ppm at 1000 kg/m3 and M = 100 g/mol gives 0.001 mol/L. At density 2000 kg/m3 the same ppm gives 0.002 mol/L.
Advertisement
Frequently asked questions
Is ppm always mg/L?
No. That approximation requires a density near 1 kg/L and a mass-based ppm definition.
Can I enter ppb?
Yes. Choose ppb; one ppm equals one thousand ppb.
Does this convert gas ppm by volume?
No. Gas mole or volume fractions require a different pressure and temperature model.