What This Calculator Does
This tool tells you how many grams of a solid solute you must weigh out to prepare a solution of a given molarity (concentration) at a chosen volume. It is essential for lab work, chemistry homework, and preparing reagents and buffers. The calculation is universal and works for any compound as long as you know its molar mass.
How to Use It
Enter three values: the target molarity in mol/L, the solution volume in liters, and the molar mass of your solute in g/mol. The calculator returns the mass of solute in grams, plus the total moles required. Dissolve that mass in solvent and dilute to the target volume to reach your concentration.
The Formula Explained
The relationship is $$\text{mass} = M \times V \times MW$$ Molarity (\(M\)) multiplied by volume in liters (\(V\)) gives the number of moles needed. Multiplying moles by the molar mass (\(MW\)) converts moles into grams. If your volume is in milliliters, divide it by 1000 before entering it as liters.
Worked Example
To make 0.5 L of a 2 mol/L sodium chloride (NaCl, molar mass 58.44 g/mol) solution: $$\text{mass} = 2 \times 0.5 \times 58.44 = 58.44 \text{ grams}$$ You would weigh out 58.44 g of NaCl and dissolve it to a final volume of 0.5 L.
FAQ
What if my volume is in mL? Convert to liters first (mL ÷ 1000) before entering it.
Where do I find molar mass? Add up the atomic masses of every atom in the chemical formula, or look it up on the compound label or a periodic table.
Does temperature matter? Molarity is defined at the final solution volume, which can vary slightly with temperature, but for routine work this calculation is sufficient.
