Concentration Converter

All concentration conversions use g/L as the base unit. These conversions assume water-based (aqueous) solutions where 1 L of water weighs 1 kg.

Key conversions:

• 1 g/L = 1,000 mg/L
• 1 g/L = 1,000,000 µg/L
• 1 g/L = 1 kg/m³
• 1 g/L = 1,000 ppm (parts per million, in water)
• 1 g/L = 1,000,000 ppb (parts per billion, in water)

Note on ppm and ppb:

• For water: 1 mg/L = 1 ppm, 1 µg/L = 1 ppb
• This is because water density is approximately 1 kg/L

Common references:

• Drinking water chlorine: about 0.2–4 mg/L (0.2–4 ppm)
• Sea water salt: about 35 g/L (35,000 ppm)

Beyond the water assumption noted above, the conversion most people get wrong is between the percentage forms. Weight/volume (w/v) is grams per 100 mL, weight/weight (w/w) is grams per 100 grams, and volume/volume (v/v) is for mixing two liquids. They give different numbers for the same solution, and a label that just says “5%” rarely tells you which one it means.

Molarity adds one more step, because it counts molecules rather than mass. Converting to or from molarity always needs the solute’s molar mass, so a 1 molar solution of a heavy compound holds far more grams per liter than a 1 molar solution of a light one. That’s why a chemist reaching for “0.1 M” and a technician measuring “10 g/L” can be describing completely different concentrations of the same substance unless they convert carefully.