Molarity Calculator
Calculate Molarity using standard chemistry formulas. Enter concentration, volume, or pH values to get instant results with step-by-step derivations.
Formula
Molarity (M) = moles (n) ÷ volume (L)
Molarity equals moles of solute divided by liters of solution. Rearrange to find moles (M×V) or volume (n÷M).
Worked Examples
Example 1: Prepare NaCl Solution
Problem:How much NaCl is needed to prepare 500 mL of 0.9% saline (approximately 0.154 M)?
Solution:Moles needed = M × V\nmoles = 0.154 M × 0.5 L = 0.077 mol\n\nMass = moles × MW\nmass = 0.077 × 58.44 = 4.5 g\n\nDissolve 4.5g NaCl in water to make 500mL
Result:4.5 g NaCl in 500 mL water
Example 2: Calculate Concentration
Problem:25 grams of glucose dissolved in 500 mL solution. What is the molarity?
Solution:Moles = mass ÷ MW\nmoles = 25 g ÷ 180.16 g/mol = 0.139 mol\n\nMolarity = moles ÷ volume\nM = 0.139 ÷ 0.5 L = 0.278 M
Result:0.278 M (278 mM)
Example 3: Dilution Calculation
Problem:Dilute 2M HCl to make 250 mL of 0.5M solution. How much stock needed?
Solution:C₁V₁ = C₂V₂\n2M × V₁ = 0.5M × 250mL\nV₁ = (0.5 × 250) ÷ 2 = 62.5 mL\n\nAdd 62.5 mL of 2M HCl to ~187.5 mL water
Result:62.5 mL of 2M stock
Frequently Asked Questions
What is molarity?
Molarity (M) is the concentration of a solution expressed as moles of solute per liter of solution. A 1M solution contains 1 mole of solute in 1 liter. Formula: M = moles ÷ volume (L).
How do I calculate molarity from mass?
First calculate moles: moles = mass (g) ÷ molar mass (g/mol). Then: Molarity = moles ÷ volume (L). For example, 5.84g NaCl (MW=58.44) in 1L = 0.1M.
What's the difference between molarity and molality?
Molarity (M) = moles/liter of solution. Molality (m) = moles/kg of solvent. Molality doesn't change with temperature since mass doesn't expand like volume.
How do I prepare a specific molarity solution?
Calculate mass needed: mass = Molarity × Volume (L) × Molar mass. For 100mL of 0.5M NaCl: 0.5 × 0.1 × 58.44 = 2.92g. Dissolve in water to final volume.