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What does this calculator estimate?
A molarity-from-mass calculator converts a weighed solute into solution concentration. Enter the solute mass, molar mass, and solution volume to get molarity and g/L.
- Moles = mass ÷ molar mass
- Molarity = moles ÷ liters
- g/L = mass ÷ liters
How to make solutions from mass
Lab work usually starts with a weighed solid, not moles. The molar mass converts grams to moles, and the volume converts moles to molarity — the two-step bridge between the balance and the flask.
Limitations to watch for
The tool assumes the solute is pure and dissolves completely. Volume is the final solution volume (solute plus solvent), not the solvent volume alone. Molar mass must match the exact formula (hydrates change it).
How to use it in practice
Weigh the solute, note the molar mass (from the periodic table or the molar mass calculator), and choose the final volume. Dissolve solute in less than the final volume, then top up to the mark.
['Enter the solute mass in grams.', 'Enter its molar mass in g/mol.', 'Enter the final solution volume in mL.']
How this calculator works
Formula
Moles = solute mass (g) ÷ molar mass (g/mol). Molarity = moles ÷ volume (L). Concentration (g/L) = solute mass ÷ volume (L).
Worked example
5.85 g of NaCl (molar mass 58.44 g/mol) dissolved to 250 mL: moles = 0.1001, so M = 0.1001 ÷ 0.25 = 0.400 M; concentration = 5.85 ÷ 0.25 = 23.4 g/L.
Assumptions to verify
- The solute is pure and fully dissolves.
- Volume is the final solution volume.
- Molar mass is accurate for the exact formula.
Frequently asked questions
How do I find molarity from mass?
Convert grams to moles (mass ÷ molar mass), then divide by liters. 5.85 g NaCl in 250 mL = 0.1001 mol ÷ 0.25 L = 0.400 M.
What is molar mass?
The mass of one mole in g/mol — for NaCl, 58.44 g/mol. It converts between grams and moles.
What is the difference between molarity and g/L?
Molarity is moles per liter (how many particles); g/L is mass per liter (how much weight). Both are shown by the tool.
Should I use final volume or solvent volume?
Final volume — the solution's total volume after dissolving, which is what volumetric flasks measure.
How do I make 1 L of a 1 M solution?
Weigh 1 mole (molar mass in grams), dissolve in ~800 mL, then add water to the 1 L mark.
Does hydration matter?
Yes — CuSO₄·5H₂O has a different molar mass than CuSO₄. Use the mass of the exact compound you're weighing.
How is this different from the molarity calculator?
That tool starts from moles; this one starts from a weighed mass and does the mole conversion for you.
Cite this tool
BoringToolsKit. “Molarity from Mass Calculator.” boringtoolskit.com/molarity-from-mass-calculator/ (reviewed 2026-08-25). Free to reference in articles, syllabi, and answer posts with a link.
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