Molarity Calculator
A free molarity calculator that solves for moles, volume, and grams — plus a molar mass parser, and instant unit conversion between mM, M, and µM. Enter any two values and calculate the third with full step-by-step working.
Enter any 2 values — the calculator solves for the third. Formula: M = n ÷ V
Molarity Calculation Report
Generated:
Molarity Formula — M = n ÷ V
Molarity (M) is defined as the number of moles of solute dissolved per litre of solution. It is the most commonly used measure of concentration in chemistry laboratories and is expressed in units of mol/L or simply M (read as "molar").
Where:
- M = Molarity (mol/L or M)
- n = Amount of solute in moles (mol)
- V = Volume of the solution in litres (L)
Worked Example — How to Find Molarity of NaCl
You dissolve 5.844 g of sodium chloride (NaCl, molar mass = 58.44 g/mol) in water to make 500 mL of solution. What is the molarity?
- Calculate moles:
n = mass ÷ molar mass = 5.844 ÷ 58.44 = 0.1 mol - Convert volume:
V = 500 mL ÷ 1000 = 0.5 L - Apply formula:
M = n ÷ V = 0.1 ÷ 0.5 = 0.2 mol/L - Answer: 0.2 M NaCl
The Molarity Triangle
The molarity triangle is a memory aid used in chemistry to remember all three rearrangements of the molarity formula. Cover the quantity you want to find — what remains is the formula to use.
Worked Examples — Common Search Questions Answered
How to Calculate Moles from Molarity
Use n = M × V. Multiply molarity by volume in litres.
Example: 2.0 M HCl in 250 mL.
V = 0.250 L
How to Get Grams from Molarity
First find moles (n = M × V), then multiply by molar mass (g = n × MM).
Example: 0.5 M NaOH in 200 mL. MM(NaOH) = 40 g/mol.
n = 0.5 × 0.2 = 0.1 mol
How to Convert mL to Moles
You need the molarity. Use n = M × V(L). Convert mL to L first by dividing by 1000.
Example: 150 mL of 0.25 M glucose.
V = 150 ÷ 1000 = 0.15 L
How to Calculate Moles from Volume
Volume alone is not enough — you need concentration too. Formula: n = M × V.
Example: 750 mL of 1.5 M H₂SO₄.
V = 0.75 L
How to Go from Molarity to Moles
Molarity × Volume = Moles. This is the most common lab calculation. Always convert volume to litres first.
Example: 3.0 M KCl, need moles in 400 mL.
How to Calculate Millimoles
1 millimole (mmol) = 0.001 mol. Multiply moles by 1000 to get mmol, or use mmol/mL = mol/L.
Example: 0.05 mol NaCl = ?
What Is the Difference Between Molar and Millimolar?
Molar (M) and millimolar (mM) are both units of concentration, but differ by a factor of 1,000. One molar (1 M) means 1 mole of solute per litre of solution. One millimolar (1 mM) means 0.001 moles per litre — or equivalently, 1 mole per 1,000 litres. So 1 M = 1,000 mM and 1 mM = 0.001 M. In biology and biochemistry, mM is common for enzyme substrates, metabolites, and drug concentrations. M is used for bulk solutions like NaCl brines or acid/base titrations.
What Does 100 mM Mean in Molar?
100 mM = 100 × 10⁻³ M = 0.1 M. To convert any mM value to M, simply divide by 1,000. So 100 mM ÷ 1,000 = 0.1 M. This is equivalent to saying your solution contains 0.1 moles of solute per litre.
How to Convert Micromolar to Molar
1 µM (micromolar) = 10⁻⁶ M. To convert µM to M, divide by 1,000,000. To convert M to µM, multiply by 1,000,000. Example: 250 µM = 250 ÷ 1,000,000 = 2.5 × 10⁻⁴ M. Micromolar concentrations are typical for hormones, growth factors, and drug-receptor interactions.
Frequently Asked Questions
Related Calculators
| Compound | g/mol |
|---|---|
| H₂O | 18.015 |
| NaCl | 58.443 |
| NaOH | 39.997 |
| HCl | 36.461 |
| H₂SO₄ | 98.079 |
| C₆H₁₂O₆ | 180.156 |
| KCl | 74.551 |
| CaCl₂ | 110.983 |
| NH₄Cl | 53.491 |