Molarity Calculator
Solve For:
✅
Result
—
Moles (n)
—
Molarity (M)
—
Volume
—
Mass (g)
—
How to Use the Molarity Calculator
Select what you want to solve for using the "Solve For" buttons at the top. Enter the known values in the remaining fields, then click Calculate. The result and all related values appear instantly.
Molarity Formula
M = n / V where n = mass (g) / MW (g/mol)
M = Molarity in mol/L | n = moles of solute | V = volume of solution in litres | MW = molecular weight in g/mol
Example Calculations
Example 1 — Find Molarity
Dissolve 5.85 g of NaCl (MW = 58.44 g/mol) in 250 mL water.
n = 5.85 / 58.44 = 0.1001 mol
M = 0.1001 / 0.25 = 0.4 M
n = 5.85 / 58.44 = 0.1001 mol
M = 0.1001 / 0.25 = 0.4 M
Example 2 — Find Mass
Prepare 500 mL of 1 M NaOH (MW = 40 g/mol).
n = 1 × 0.5 = 0.5 mol
mass = 0.5 × 40 = 20 g
n = 1 × 0.5 = 0.5 mol
mass = 0.5 × 40 = 20 g
Example 3 — Find Volume
How much volume for 0.2 mol of 2 M HCl?
V = n / M = 0.2 / 2 = 0.1 L = 100 mL
V = n / M = 0.2 / 2 = 0.1 L = 100 mL
Example 4 — Find Moles
How many moles in 750 mL of 0.5 M glucose?
n = M × V = 0.5 × 0.75 = 0.375 mol
n = M × V = 0.5 × 0.75 = 0.375 mol
About Molarity in the Laboratory
Molarity (symbol M) is the most common unit of concentration used in chemistry and biotechnology laboratories. It is defined as the number of moles of solute dissolved per litre of solution.
Molarity is essential for preparing reagents, buffers, media and standard solutions. Common biotechnology applications include preparing NaCl solutions, phosphate buffers (PBS), gel electrophoresis buffers (TAE, TBE) and cell culture media.
Common Molecular Weights for Reference
NaCl — 58.44 g/mol
Used in PBS, saline solutions, electrophoresis buffers and cell culture.
NaOH — 40.00 g/mol
Used for pH adjustment, buffer preparation and cleaning procedures.
Tris — 121.14 g/mol
Common buffer component in DNA/RNA extraction and electrophoresis.
EDTA — 372.24 g/mol
Chelating agent used in TE buffer, DNA extraction and cell lysis.
Other Lab Calculators