Molarity Calculator
Calculate molarity, moles, mass, or volume of any solution. Includes a dilution calculator (C₁V₁ = C₂V₂), a 20+ compound molar mass library, and step-by-step solutions.
M = n/V
Formula
4
Solve Modes
C₁V₁ = C₂V₂
Dilution
20+
Compounds
Molarity Calculator
Solve for any variable
Quick Compound Select
M = n ÷ V or mass ÷ (MM × V)Molarity
0.2002
mol/L (M)
0.1001 mol of solute dissolved
REFERENCE DATA
Molar Masses of Common Compounds
Use these values as input for your molarity calculations.
| Compound | Molar Mass (g/mol) | Formula | Category | Common Use |
|---|---|---|---|---|
| Water | 18.015 | H₂O | Solvent | Universal solvent, reference |
| Sodium chloride | 58.443 | NaCl | Salt | Saline solutions, electrolyte |
| Sodium hydroxide | 39.997 | NaOH | Base | Titrations, pH adjustment |
| Hydrochloric acid | 36.458 | HCl | Acid | Acid solutions, titrations |
| Sulfuric acid | 98.072 | H₂SO₄ | Acid | Electrochemistry, synthesis |
| Acetic acid | 60.052 | CH₃COOH | Acid | Buffer solutions |
| Glucose | 180.156 | C₆H₁₂O₆ | Organic | Biology, cell culture |
| Sucrose | 342.297 | C₁₂H₂₂O₁₁ | Organic | Density gradients |
| Ethanol | 46.068 | C₂H₅OH | Organic | Solvent, sterilization |
| Potassium chloride | 74.551 | KCl | Salt | Electrolyte solutions |
| Calcium chloride | 110.978 | CaCl₂ | Salt | Cell biology, desiccant |
| Sodium bicarbonate | 84.007 | NaHCO₃ | Salt | Buffer, pH 8.3 reference |
| Ammonia | 17.031 | NH₃ | Base | pH adjustment |
| EDTA (disodium) | 336.206 | C₁₀H₁₄N₂Na₂O₈ | Organic | Chelating agent, biology |
| Phosphoric acid | 97.994 | H₃PO₄ | Acid | Buffer systems |
| Potassium hydroxide | 56.106 | KOH | Base | Saponification, titrations |
| Sodium carbonate | 105.988 | Na₂CO₃ | Salt | Standardizing acids |
| Magnesium sulfate | 120.366 | MgSO₄ | Salt | Growth media, drying agent |
| Potassium nitrate | 101.103 | KNO₃ | Salt | Ionic strength buffers |
| Citric acid | 192.124 | C₆H₈O₇ | Acid | Buffer, food chemistry |
| Urea | 60.056 | CH₄N₂O | Organic | Protein denaturation |
| Methanol | 32.042 | CH₃OH | Solvent | Solvent, fixative |
⚠️ Always Add Acid to Water — Never Water to Acid
When preparing dilute acid solutions (especially H₂SO₄), always add the concentrated acid slowly to water while stirring. Adding water to concentrated acid can cause violent, exothermic splattering. Cool and mix well to final volume after the solution cools. Always wear eye protection and appropriate PPE when handling concentrated acid.
🧪 Concentration Units Compared
- Molarity (M): mol/L. Changes with temperature (volume changes). Most common in chemistry labs.
- Molality (m): mol/kg solvent. Temperature-independent. Used for colligative properties (boiling point, freezing point depression).
- % w/v: g/100 mL. Simple for practical use. Used in clinical settings (e.g. 0.9% NaCl saline = 9 g/L).
- ppm / ppb: mg/L (µg/L). Used for trace concentrations in environmental science.
🩺 Molarity in Biology
In biology and medicine, concentrations are often in mM (millimolar) or µM (micromolar). Blood glucose is roughly 5 mmol/L. Physiological saline is 154 mM NaCl (0.154 M). Cell culture media contain dozens of compounds at carefully controlled millimolar concentrations.
The intracellular K⁺ concentration is ~150 mM; extracellular Na⁺ is ~145 mM. These precisely maintained gradients drive nerve impulses and cell-volume regulation — making accurate molarity calculations essential in biomedical research.
How to Calculate Molarity — All Four Formulas
Molarity is the most fundamental concentration unit in chemistry. The core relationship M = n/V (moles per liter) can be rearranged to solve for any of the four key variables: molarity, moles, mass, or volume — once you know the other three.
🧮 The Four Core Formulas
Molarity: M = n ÷ V or M = mass ÷ (MM × V) Moles: n = mass ÷ MM Mass: mass = M × V × MMWhere: M = Molarity (mol/L), n = moles of solute (mol), V = volume of solution in Liters, MM = Molar mass (g/mol)Example 1 — Find molarity: Dissolve 5.85 g NaCl (MM = 58.44) in 500 mL water. n = 5.85 ÷ 58.44 = 0.1001 mol. M = 0.1001 ÷ 0.5 = 0.2 mol/LExample 2 — Find mass needed: Prepare 250 mL of 0.1 mol/L NaOH. mass = 0.1 × 0.25 × 39.997 = 1.0 g💧 The Dilution Formula: C₁V₁ = C₂V₂
C₁V₁ = C₂V₂, where C₁ (initial/stock) concentration V₁ = volume of stock solution to take, C₂ = final (diluted) concentration V₂ = final total volume. Moles are conserved: C₁V₁ = moles taken = C₂V₂.
Example: Make 200 mL of 0.25 M HCl from 12 M stock. V₁ = (C₂ × V₂) ÷ C₁ = (0.25 × 200) ÷ 12 = 4.17 mL of stock. Add 4.17 mL of 12 M HCl → make up to 200 mL total volume of water to add = 195.83 mL.📏 Volume Unit Conversions
1 L = 1000 mL = 10 dL = 1,000,000 µL To convert to Liters for M = n/V: mL ÷ 1000, dL ÷ 10 (500 mL = 0.5 L), µL ÷ 1,000,000, or L stays as-isMolarity vs Other Concentration Units
Understanding when to use molarity versus other concentration expressions matters in chemistry and biology, since lab protocols, safety sheets, and clinical references don't all use the same unit.
Converting % w/v to Molarity
% w/v (percent weight/volume) = grams of solute per 100 mL of solution ÷ 10 = g/L. To convert to molarity: M = (%w/v × 10) ÷ Molar Mass. Example: 37% HCl (MW = 36.46 g/mol): M = (37 × 10) ÷ 36.46 ≈ 10.15 M. For concentrated solutions, density must also be factored in.
Converting ppm to Molarity
For dilute aqueous solutions ppm ≈ mg/L. To convert: M = ppm ÷ (Molar Mass × 1000). Example: 50 ppm NaCl (MW = 58.44): M = 50 ÷ (58.44 × 1000) ≈ 0.000856 M = 0.856 mM. Used environmental and trace analysis.
Why Molarity Changes with Temperature
Molarity is based on volume, which expands when heated. So the same amount of solute occupies more volume as the solution warms, making molarity slightly lower at 80°C than the same 1 M solution prepared at 20°C. For temperature-sensitive work, molality (mol/kg solvent) is preferred since mass doesn't change with temperature. For most lab work at room temperature, this difference is negligible.
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