Tip: use positive numbers only. This tool is for educational and laboratory planning use.
What this molecular weight concentration calculator does
This calculator helps you quickly move between the values that matter most during solution prep: molecular weight (g/mol), mass, volume, and concentration. Instead of manually rearranging formulas each time, you choose a mode and calculate the missing value instantly.
It is useful for chemistry labs, molecular biology workflows, buffer preparation, and stock solution planning. Whether you need to make a 10 mM reagent, back-calculate concentration from a weighed sample, or estimate molecular weight from known data, this tool keeps the math consistent.
Core formulas used
1) Concentration (molarity)
M = mass (g) / [MW (g/mol) × volume (L)]
2) Mass required
mass (g) = M (mol/L) × MW (g/mol) × volume (L)
3) Volume required
volume (L) = mass (g) / [MW (g/mol) × M (mol/L)]
4) Molecular weight
MW (g/mol) = mass (g) / [M (mol/L) × volume (L)]
How to use this tool correctly
- Select the value you want to calculate from the dropdown.
- Enter the three required known values.
- Set units carefully (g vs mg, L vs mL, M vs mM).
- Click Calculate to see converted outputs and the final answer.
Why unit conversion matters
Most calculation errors come from unit mismatch. For example, entering 500 mL as if it were 500 L causes a 1000× error. This page automatically converts:
- Mass: g, mg, µg
- Volume: L, mL, µL
- Concentration: M, mM, µM, nM
Example workflow
Prepare 100 mL of 25 mM glucose (MW 180.16 g/mol)
- Mode: Mass needed
- Concentration: 25 mM
- Volume: 100 mL
- MW: 180.16 g/mol
The calculator returns approximately 0.4504 g glucose (or 450.4 mg).
Common mistakes to avoid
- Using molecular weight in the wrong units (must be g/mol).
- Typing concentration in mM while leaving unit set to M.
- Forgetting that very small volumes can produce very high concentrations.
- Rounding too aggressively before final prep calculations.
FAQ
Is this the same as a molarity calculator?
Yes. This is a molarity and solution preparation calculator with extra flexibility to solve for mass, volume, or molecular weight.
Can I use this for protein solutions?
Yes, if you know the molecular weight of the protein and are working in molar concentration terms. For activity-based dosing, use assay-specific methods.
Is this suitable for clinical or pharmaceutical decisions?
Use caution. This tool is for educational and lab planning use, not as a substitute for validated clinical protocols or GMP documentation.