Molarity Calculator: what this tool is for
The online molarity calculator helps you prepare laboratory chemical solutions with accurate concentrations by calculating the required solute mass to weigh, target molarity, or necessary solvent volume.
In chemistry, biochemistry, and molecular biology, molarity (symbol C or M) is defined as the amount of substance (in moles) dissolved per liter of solution (mol/L). It is the standard metric for formulating buffers, culture media, and analytical reagents.
The tool solves the fundamental formula C = n / V = m / (M × V) in all directions: calculate the precise mass to weigh on a balance (m = C × V × M), the resulting molar concentration, or the maximum volume prepared from a given mass.
The solute's molar mass can be entered manually or calculated dynamically from its chemical formula (e.g., NaCl, NaOH, CuSO4·5H2O) using the integrated IUPAC periodic table.
To streamline benchtop laboratory workflows, the calculator automatically formats a step-by-step preparation protocol ready to copy, print, and execute.
No file stored
Nothing is saved on our servers, during or after processing.
Local processing
The computation runs in your browser whenever the technology allows it.
Instant result
No waiting and no export queue: the result appears live.
Free, no account
No sign-up, no daily limit and no intrusive ads.
What this tool gives you
Multi-Directional Solution Calculation
Solve for solute mass, molarity, solution volume, or total moles without needing to manually rearrange algebraic equations.
Chemical Formula Auto-Detection
Type any chemical reagent formula (e.g., Tris, NaCl, EDTA) to resolve its exact molar mass and immediately compute the required mass to weigh.
Automatic Multi-Unit Conversion
Work seamlessly across grams, milligrams, micrograms, or kilograms, as well as liters, milliliters, and microliters with instant scaling.
Practical Laboratory Protocol
Generate clear laboratory instructions covering weighing, partial beaker dissolution, quantitative volumetric flask transfer, and meniscus adjustment.
Real-world examples
Typical solution preparation benchmarks in chemistry, biology, and pharmacology labs.
Preparing 500 mL of 0.2 M NaCl solution
To prepare 500 mL of a sodium chloride solution (NaCl, M = 58.44 g/mol) at 0.2 M, calculate mass m = 0.2 mol/L × 0.5 L × 58.44 g/mol = 5.844 g of NaCl to weigh.
Verifying molarity from a weighed reagent
If 10.0 g of sodium hydroxide (NaOH, M = 40.00 g/mol) is dissolved in a 250 mL volumetric flask, the resulting molar concentration is C = 10 / (40 × 0.25) = 1.00 mol/L.
How to use Molarity Calculator
Select your target variable
Choose what to calculate: solute mass to weigh, molar concentration, solution volume, or total moles.
Enter the solute formula or molar mass
Type the chemical formula to auto-calculate molar mass from IUPAC tables, or type the molar mass directly in g/mol.
Input known parameters
Enter the desired concentration and final solution volume with their corresponding unit dropdowns (M, mM, mL, L).
Follow the generated protocol
Review the calculated mass to weigh and copy the step-by-step laboratory instructions for benchtop execution.
Tips and mistakes to avoid
Always check for hydrated salt forms
If using a hydrated salt (e.g., CuSO4·5H2O instead of anhydrous CuSO4), the molar mass is higher. Always use the hydrated formula to weigh the correct mass.
Dissolve in a beaker before volumetric flask transfer
Dissolve the solid in 60-80% of the solvent volume in a beaker first, then transfer quantitatively to the volumetric flask and fill to the mark.
Account for reagent purity percentage
If your commercial chemical bottle indicates 98% assay purity, divide the calculated mass by 0.98 to weigh the correct amount of active substance.
Avoid : Confusing molarity (mol/L) with molality (mol/kg solvent)
Molarity is relative to total solution volume in liters, whereas molality is relative to pure solvent mass in kilograms.
Avoid : Adding solvent directly to powder without a volumetric flask
Dissolving solid changes the total solution volume. Adding 500 mL of water to 50 g of salt will not produce exactly 500 mL of final solution.
Frequently asked questions
Answers to the questions people ask about Molarity Calculator.
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Updated on August 2026. See all tools