Home › Unit Converter › Pressure Pressure Converter — 11 units available From ⊘ ⇄ To ⊘ Formula — Quick Reference — click row to apply UnitResultEquivalent 🧪 Concentration Converter 💧 Liquid / Aqueous 💨 Gas / Air Solution Density (g/mL) Default: water = 1.000 g/mL Molar Mass (g/mol) optional Required for mol/L ↔ other Temp (°C) & Pressure (atm) Vm = 24.45 L/mol @ 25°C, 1 atm ppm (mg/kg) mg/L mg/m³ ppb (µg/kg = µg/L*) µg/m³ % w/w % w/v g/L g/m³ mol/L (M) mmol/L (mM) ppmv (vol/vol gas) Liquid mode (water, ρ=1.000 g/mL): ppm = mg/L ÷ ρ | % w/w = ppm ÷ 10,000 | % w/v = (ppm × ρ) ÷ 100,000