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About this tool
Calculate dilution concentrations and volumes with C1V1 = C2V2, or find molarity from a solute's mass and molar mass.
The Dilution & Molarity Calculator solves the two arithmetic steps behind most bench solutions: the dilution equation C₁V₁ = C₂V₂, rearranged to give the final volume V₂ = C₁V₁ / C₂, and molarity from mass, M = (mass ÷ molar mass) ÷ volume in litres. Alongside the answer it reports the diluent you actually have to add (V₂ − V₁), the dilution factor C₁/C₂, and the mole count, so you can check the working rather than trusting one number. It is an arithmetic aid for students and lab users — it does not know your reagent's purity, hydration state or hazards.
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On the C₁V₁ = C₂V₂ mode, enter Stock concentration C₁, Stock volume V₁ (mL) and Final concentration C₂ — the 'Dilute 2 M to 0.5 M' preset loads 2, 25 mL and 0.5.
Switch to the Molarity from mass mode to work the other calculation instead: Solute mass (g), Molar mass (g/mol) and Solution volume (L), with the NaCl example preset filling 5.844 g at 58.44 g/mol in 1 L.
Read the final volume in mL with Diluent to add, Dilution factor and the C₁V₁ product listed as rows (or mol/L with Moles for the mass mode), then Copy or Download it as dilution-molarity-calculator.txt.
The diluent line gives V₂ − V₁ directly, which is the number you pipette — the step most people do in their head and get wrong.
Switch between C₁V₁ = C₂V₂ and molarity-from-mass without re-entering the problem in a different tool.
Moles, molar mass, volume, dilution factor and the C₁V₁ product are listed as rows so a wrong input is obvious at a glance.
Rearrange it to V₂ = C₁V₁ / C₂ to find the volume your diluted solution must end up at, then subtract V₁ to get the solvent to add. Taking 25 mL of 2 M stock to 0.5 M gives V₂ = (2 × 25) / 0.5 = 100 mL, so you add 75 mL of diluent — a 4× dilution.
Divide the mass by the molar mass to get moles, then divide by the solution volume in litres. 5.844 g of sodium chloride at 58.44 g/mol is 0.1 mol, which in 1 L is 0.1 mol/L.
No — C₁ and C₂ only have to match each other. The equation is a ratio, so mg/mL, % w/v, X-strength buffer or mol/L all work as long as both concentrations use the same unit; the volume answer comes back in the same unit as V₁, which this page labels in millilitres.
Usually hydration, purity or volume additivity. Hydrated salts carry water in their formula mass (for example CuSO₄·5H₂O is 249.7 g/mol, not 159.6), reagents below 100% assay contribute less solute than they weigh, and dissolving solute changes the total volume — which is why you make up to the mark in a volumetric flask rather than adding solvent to a fixed volume. Follow your lab's safety and glassware procedures; this page only does the arithmetic.
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