Molarity From Mass Calculator
This molarity from mass calculator converts the mass of a dissolved solute into molar concentration. Enter the mass (g, mg, µg, or kg), molar mass (g/mol), and solution volume (L or mL) to instantly compute molarity (M). Below you'll find the mass-to-molarity formula, step-by-step instructions, and worked examples.
Molarity From Mass Calculator
Mass → Moles → Molarity
M = mass / (MW × V) What is Molarity From Mass?
Molarity from mass determines the molar concentration of a solution when you know the mass of solute dissolved. It answers the question: if I dissolve X grams of substance in Y liters of solution, what is the molarity?
The method requires three values: the mass of solute in grams, the molar mass (molecular weight) of the solute in g/mol, and the volume of the solution in liters.
This is the most common way to calculate molarity in laboratories — weigh a substance, dissolve it in a measured volume, and compute the resulting concentration.
Molarity From Mass Formula
The molarity from mass formula has two steps:
First, convert mass to moles by dividing the mass of the solute by its molar mass. Then divide by volume:
This gives you the molarity directly from weight measurements.
The calculator accepts mass in g, mg, µg, or kg, volume in L, mL, or µL, and returns molarity in M, mM, µM, nM, or smaller units.
How to Calculate Molarity From Mass
Follow these 6 steps to calculate molarity when you know the mass of solute:
- Weigh the solute on an analytical balance. Record the mass in grams (g).
- Look up the molar mass of the substance. For NaCl it is 58.44 g/mol; for glucose (C₆H₁₂O₆) it is 180.16 g/mol.
- Measure the total volume of the solution (not the solvent alone) in liters.
- Calculate moles: divide mass by molar mass → moles = mass ÷ MW.
- Calculate molarity: divide moles by volume → M = moles ÷ V.
- Verify using this calculator. Enter mass, molar mass, and volume to confirm your result.
Molarity From Mass Examples
Here are 3 worked examples showing how to convert mass to molarity:
Example 1: Dissolve 29.22 g NaCl (MW = 58.44 g/mol) in 500 mL of solution. Moles = 29.22 ÷ 58.44 = 0.5 mol. Volume = 0.5 L. Molarity = 0.5 ÷ 0.5 = 1.0 M.
Example 2: Dissolve 18.02 g glucose (MW = 180.16 g/mol) in 1 L. Moles = 18.02 ÷ 180.16 = 0.1 mol. Molarity = 0.1 ÷ 1 = 0.1 M = 100 mM.
Example 3: Dissolve 5 mg BSA (MW = 66,500 g/mol) in 10 mL. Mass = 0.005 g. Moles = 0.005 ÷ 66500 = 7.52 × 10⁻⁸ mol. Volume = 0.01 L. Molarity = 7.52 µM.
Molarity Calculator Tools
Explore our collection of 20 specialized molarity calculators. Each tool is designed for a specific type of calculation with its own unique input fields and formulas.
FAQs
How do you calculate molarity from mass?
Divide the mass (g) by the molar mass (g/mol) to get moles, then divide by volume (L). Formula: M = mass / (molar mass × volume).
What mass is needed for a 1 M NaCl solution in 500 mL?
Mass = M × molar mass × volume = 1 × 58.44 × 0.5 = 29.22 g of NaCl.
Can I use milligrams instead of grams?
Yes. Convert mg to g by dividing by 1000, or use the calculator's unit dropdown to select mg directly.
What units does the Molarity From Mass Calculator support?
The molarity from mass calculator supports mass units (g, mg, µg, kg), volume units (L, mL, µL, gal), molar mass (g/mol, kg/mol), and molarity units (M, mM, µM, nM, pM, fM, aM).
Is the Molarity From Mass Calculator free to use?
Yes. The molarity from mass calculator is 100% free, requires no sign-up, and works on all devices. All calculations are performed instantly in your browser.