Molarity Calculator
Use this tool to calculate molarity (M), moles (n), or solution volume (V).
where M = molarity (mol/L), n = moles of solute (mol), V = volume of solution (L)
What Is Concentration in Molarity?
Concentration tells you how much solute is dissolved in a certain amount of solution. Molarity is one of the most common concentration units in chemistry and is written as M, meaning moles per liter (mol/L).
If a solution has a molarity of 2.0 M, that means there are 2.0 moles of solute in each 1 liter of solution. Molarity is used in lab experiments, pharmaceutical formulation, industrial mixing, and educational chemistry problems.
The Molarity Formula
Core equation
M = n / V
- M = molarity in mol/L
- n = moles of solute
- V = volume of solution in liters
Rearranged forms
- n = M × V (to find moles)
- V = n / M (to find volume)
This calculator supports all three forms, so you can solve for whichever variable you need.
How to Use This Calculator
- Choose what you want to calculate: molarity, moles, or volume.
- Enter the known values in the input boxes.
- Select the correct volume unit (L or mL).
- Click Calculate to view the result and calculation steps.
Tip: If your volume is in milliliters, the calculator automatically converts it to liters before applying the formula.
Worked Examples
Example 1: Calculate molarity
You dissolve 0.75 mol NaCl in 300 mL solution.
- Convert volume: 300 mL = 0.300 L
- M = n / V = 0.75 / 0.300 = 2.50 mol/L
Answer: 2.50 M
Example 2: Calculate moles
A 1.2 M solution has a total volume of 2.0 L.
- n = M × V = 1.2 × 2.0 = 2.4 mol
Answer: 2.4 mol
Example 3: Calculate volume
You need 0.40 mol of solute at 0.20 M concentration.
- V = n / M = 0.40 / 0.20 = 2.0 L
- In mL: 2.0 L = 2000 mL
Answer: 2.0 L (2000 mL)
Common Mistakes to Avoid
- Using mL directly in the formula without converting to liters.
- Confusing moles with grams (convert mass to moles first if needed).
- Using solute volume instead of total solution volume.
- Rounding too early in multi-step calculations.
Why Molarity Matters
Molarity is foundational in stoichiometry and solution chemistry. It helps you:
- Prepare standard lab solutions accurately
- Perform dilution calculations
- Predict reaction yields
- Compare concentration strength across mixtures
Quick FAQ
Is molarity temperature-dependent?
Yes. Volume changes with temperature, so molarity can change slightly as temperature changes.
Can molarity be less than 1?
Absolutely. For example, 0.05 M means 0.05 mol per liter.
What if I only have grams of solute?
Convert grams to moles first using: moles = mass (g) / molar mass (g/mol), then use this molarity calculator.