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FREE RESEARCH CALCULATOR

Protein Molarity Calculator

Convert protein concentration in mg/mL and molecular weight in kDa to µM and nM.

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CORE EQUATIONM = (g/L) ÷ (g/mol)
WHAT IT DOES

From formula to a bench-ready decision.

Convert a protein mass concentration into molar concentration using the protein molecular weight.

Tossora Lab keeps units, intermediate values, and practical preparation checks visible so a mathematically correct answer is easier to translate into an experimental workflow.

BUILT-IN CHECKS

What Tossora Lab checks.

  • Makes the molecular-weight assumption explicit.
  • Returns both µM and nM.
  • Rejects zero or negative physical inputs.
BENCH NOTES

Before you use the result.

  • Use the molecular weight of the actual construct or species being quantified.
  • Account for tags, conjugates, oligomeric state, or other mass changes when they are relevant to the calculation.

Research use only. Verify critical calculations, reagent specifications, route or instrument limits, and procedures against your approved protocol and institutional requirements.

COMMON USES

When this calculator is useful.

  • Converting a purified-protein concentration from mg/mL to µM.
  • Planning molar-equivalent protein inputs from a mass concentration.
  • Checking how molecular weight changes the molarity of the same mg/mL solution.
WORKED CONTEXT

Example: 1 mg/mL of a 50 kDa protein

Because 1 mg/mL equals 1 g/L, dividing by 50,000 g/mol gives 0.00002 mol/L, or 20 µM.

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FAQ

Questions researchers often ask.

Why does a larger protein have a lower molarity at the same mg/mL?

Molarity counts molecules rather than mass. A larger molecular weight means fewer moles are present in the same mass concentration.

Should I use monomer or complex molecular weight?

Use the molecular species that matches the question you are calculating. For a defined oligomeric complex or conjugate, the relevant mass may differ from the monomer sequence mass.

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