Free AI Molarity Calculator
Calculate molarity, mass, volume, or dilution for your lab solutions in seconds. Perfect for chemistry students, lab technicians, and researchers across the United States.
Mass from Volume & Concentration
Calculate how much solute (in grams) you need to prepare a solution.
Mass Required
— g
Input:
About Our Free Molarity Calculator
This free Molarity Calculator helps you quickly determine the molarity, mass, volume, or dilution needed to prepare chemical solutions.
Molarity (M) represents the number of moles of solute per liter of solution, making it one of the most essential concepts in chemistry and laboratory work.
The AI tool simplifies everyday stoichiometry by performing instant calculations based on molar mass, molecular weight, and standard unit conversions.
It supports common laboratory units such as M, mM, µM for concentration and g, mg, L, mL for mass and volume, allowing you to work without manual formulas.
Designed with a clean and responsive interface, this calculator works smoothly on both mobile and desktop devices.
It’s ideal for students, educator, and researchers preparing solutions for chemistry classes, laboratory experiments, or scientific research.
Molarity Formula (With Examples and Full Explanation)
Here are the core formulas used to calculate molarity, mass, volume, and dilution in chemistry and laboratory work.
1. Molarity from Mass and Volume
M = Mass (g) ÷ [Molar Mass (g/mol) × Volume (L)]
2. Mass from Molarity and Volume
Mass (g) = M × Volume (L) × Molar Mass (g/mol)
3. Volume from Mass and Molarity
Volume (L) = Mass (g) ÷ [M × Molar Mass (g/mol)]
4. Dilution Formula (C₁V₁ = C₂V₂)
V₁ = (C₂ × V₂) ÷ C₁
Worked Examples
Example 1: Finding Mass for a NaCl Solution
Problem: How many grams of NaCl (58.44 g/mol) are needed for 250 mL of 0.5 M solution?
Step:
Mass = M × V × Molar Mass
Mass = 0.5 × 0.250 × 58.44
Mass = 7.305 g
Example 2: Calculating Molarity of a Glucose Solution
Problem: 18 g glucose (180.16 g/mol) in 500 mL solution — what is the molarity?
Step:
M = Mass ÷ (Molar Mass × Volume)
M = 18 ÷ (180.16 × 0.5)
M = 0.2 M
Example 3: Diluting a Stock HCl Solution
Problem: Prepare 100 mL of 0.1 M HCl from a 1 M stock.
Step:
V₁ = (C₂ × V₂) ÷ C₁
V₁ = (0.1 × 100) ÷ 1
V₁ = 10 mL
Take 10 mL stock and dilute to 100 mL total.
How to Calculate Molarity: A Step-by-Step Guide
The calculator includes four calculation modes — Mass, Volume, Molarity, and Dilution. Follow the steps below to use each mode correctly and get accurate results for your chemical solutions.
A. Calculate Mass from Volume & Concentration
- Click the Mass tab in the calculator.
- Enter the desired concentration and choose the unit (M, mM, µM).
- Enter the formula weight / molar mass of your compound in g/mol.
- Type the volume of solution you want to prepare and select L or mL.
- Press Calculate to see the mass required in grams.
B. Calculate Volume from Mass & Concentration
- Open the Volume tab.
- Enter the mass of solute you have and choose g or mg.
- Enter the formula weight / molar mass in g/mol.
- Type your target concentration and select the unit (M, mM, µM).
- Click Calculate to get the volume needed in both L and mL.
C. Calculate Molarity from Mass & Volume
- Select the Molarity tab.
- Enter the mass of solute dissolved and choose g or mg.
- Enter the formula weight / molar mass in g/mol.
- Type the total solution volume and select L or mL.
- Hit Calculate to see the molarity in mol/L (M).
D. Dilute a Stock Solution (C₁V₁ = C₂V₂)
- Go to the Dilution tab.
- Enter the stock concentration (C₁) and choose the unit.
- Enter the desired concentration (C₂) for your final solution.
- Type the final volume (V₂) that you want to prepare and select L or mL.
- Click Calculate to find the stock volume required (V₁) for dilution.
Molarity Formulas and Examples
1. Molarity from Mass and Volume:
Molarity (M) = Mass (g) ÷ [Formula Weight (g/mol) × Volume (L)]
2. Mass from Molarity and Volume:
Mass (g) = Molarity (M) × Volume (L) × Formula Weight (g/mol)
3. Volume from Mass and Molarity:
Volume (L) = Mass (g) ÷ [Molarity (M) × Formula Weight (g/mol)]
4. Dilution Formula:
C₁ × V₁ = C₂ × V₂ → V₁ = (C₂ × V₂) ÷ C₁
Worked Examples
Example 1: Finding Mass for a NaCl Solution
Problem: How many grams of NaCl (formula weight = 58.44 g/mol) are needed to prepare 250 mL of a 0.5 M solution?
Solution:
Mass = Molarity × Volume × Formula Weight
Mass = 0.5 M × 0.250 L × 58.44 g/mol
Mass = 7.305 g
Example 2: Calculating Molarity of a Glucose Solution
Problem: What is the molarity of a solution containing 18 g of glucose (formula weight = 180.16 g/mol) dissolved in 500 mL?
Solution:
Molarity = Mass ÷ (Formula Weight × Volume)
Molarity = 18 g ÷ (180.16 g/mol × 0.500 L)
Molarity = 0.2 M
Example 3: Diluting a Stock HCl Solution
Problem: You have a 1 M HCl stock and need 100 mL of 0.1 M HCl. How much stock do you need?
Solution:
V₁ = (C₂ × V₂) ÷ C₁
V₁ = (0.1 M × 100 mL) ÷ 1 M
V₁ = 10 mL
Take 10 mL of stock and add water to reach 100 mL total.
Why Molarity Is Important in Chemistry
Accurate molarity calculations are fundamental to successful experiments across all chemistry disciplines:
- Education: In US high schools and colleges, molarity is a core concept. Students learn to prepare solutions for titrations, reaction studies, and analytical experiments.
- Pharmaceutical & Biology Labs: Precise concentrations are critical in drug development, biochemistry research, and clinical diagnostics. Incorrect molarity can lead to failed experiments or safety hazards.
- Research & Industry: From chemical synthesis to quality control, industrial labs rely on accurate solution preparation. Reproducibility depends on consistent concentrations.