⚖️ Concentration Converter
Convert between mg/mL, μg/mL, ng/mL, molarity (mol/L), mmol/L and % w/v. Click any result to copy it.
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mg/mL, μg/mL, ng/mL, mol/L, mmol/L, μmol/L and % w/v all in one place.
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Frequently asked questions
Why do some conversions need molecular weight (MW)?
Converting between a mass-based unit (like mg/mL) and a molar unit (like mol/L or mmol/L) requires knowing the molar mass of the solute, since molarity depends on the number of moles present, not just the mass. Mass-to-mass conversions (like mg/mL to % w/v) don't require MW since they don't involve moles.
What does % w/v actually mean?
% w/v (weight/volume) expresses concentration as grams of solute per 100 mL of solution — for example, 5% w/v means 5 g of solute dissolved in enough solvent to make 100 mL of final solution. It's distinct from % w/w (weight/weight), which uses total solution mass rather than volume in the denominator.
Can I convert between mg/mL and molarity without knowing the exact molecular weight?
No — an accurate molar mass is required for any conversion involving molarity or mmol/L. Using an incorrect or approximate MW (e.g. for a salt vs. its free base/acid form) will introduce a proportional error into the molar concentration result.
Accuracy & how this is derived
Derivation: Mass-based conversions use direct unit scaling (e.g. mg to µg). Molar conversions use the relationship moles = mass / molecular weight, then molarity = moles / volume, applied algebraically to convert between any two supported concentration units.
Validated against: Standard concentration unit definitions used throughout analytical and general chemistry.
⚠️ For educational and research support only — verify critical results independently before use in regulated, clinical, or publication-bound work.
✔ Last updated: July 2026 · Report an error
Converting concentration units in pharmaceutical and biological labs
Concentration unit conversion is required when protocols from different sources use different systems. To convert mg/mL to mol/L: divide by MW (g/mol) and multiply by 1000. To convert mol/L to µmol/L: multiply by 10⁶. % w/v = g per 100 mL = 10 mg/mL. Note that % v/v (e.g. 70% ethanol) is not the same as % w/v — ethanol volumes do not add linearly to water. Always state the molecular weight used for molar conversions in your methods section.