Concentration Converter
Convert between mass concentration (mg/mL) and molar concentration (mM).
Required for cross-type conversions (mg/mL ↔ mM).
Learn more
What it does
This converter switches between mass-per-volume units (mg/mL, μg/mL, g/L) and molar units (M, mM, μM, nM). You need the compound's molar mass only when crossing between the two types. Protocol writers freely mix the two conventions — antibody stocks are often quoted in mg/mL while inhibitor working solutions are quoted in µM — so converting between them is a daily bench task.
How it works
Molarity (M) = mass (g) / molar mass (g/mol) / volume (L). For mg/mL: M = (mg/mL) / molar mass / 1000. Reverse: mass/volume = molarity × molar mass. Same-type conversions (e.g. mM ↔ μM) are pure scaling and need no molar mass. The conversion only makes sense with the molar mass of the actual solute species. For hydrated salts, decide whether your stock is quoted as anhydrous or hydrated (e.g. anhydrous CaCl₂ 110.98 vs CaCl₂·2H₂O 147.01 g/mol) — the wrong choice shifts the true concentration by 25% or more.
Worked example
1 mg/mL of BSA (MW 66,500 g/mol) → 1 / 66500 / 1000 = 1.50×10⁻⁵ M = 15.0 μM. To make 10 mL at 15 μM, dissolve 1 mg BSA in 10 mL. Conversely, 100 µM of that BSA corresponds to 100×10⁻⁶ × 66500 = 6.65 mg/mL. Notice how a large protein can be micromolar while still sitting at several mg/mL.
When to use it
Use it to prepare buffers and stock solutions, convert assay concentrations between mg/mL and µM, and reconcile protocols that mix mass-based and molar units. It also helps when papers report ELISA or inhibitor data in one unit while your stock is in the other, and when dosing cell-culture additives consistently across experiments.
FAQ
- How do I convert mg/mL to molarity (M or mM)?
- To convert mg/mL to molarity, you need the compound's molar mass (g/mol). Formula: M = (mg/mL) / molarMass / 1000. For mM, multiply M by 1000. Enter the value, choose mg/mL → M (or mM) in the converter above, and provide the molar mass.
- How do I convert mM to mg/mL?
- To convert mM to mg/mL, use the molar mass. Formula: mg/mL = mM × molarMass / 1000. Select mM → mg/mL in the converter, enter the value and molar mass, and the result updates instantly.
- Can I convert between M and mg/mL directly?
- Yes. Cross-type conversions between molar units (M, mM, μM, nM) and mass-per-volume units (mg/mL, μg/mL, g/L) require the molar mass. The converter will prompt you to enter it when needed.
- What units can I convert between?
- Mass/volume units (mg/mL, μg/mL, g/L) and molar units (M, mM, μM, nM). Conversions within the same family are direct; crossing between mass and molar needs the molar mass.