Enter the two known quantities
Start by choosing what to solve for in Solve for. The calculator hides that quantity's field, so you enter the other two values. It converts amount to mol, volume to liters, and molarity to mol/L before applying the selected equation.
- In Solve for, choose Molarity (M), Amount of solute (n), or Volume of solution (V).
- Enter the other two values in Amount of solute, Volume of solution, or Molarity, then choose each field's Unit.
- If Amount of solute uses g (mass) or mg (mass), enter a positive Molar mass of solute (g/mol).
- Select Calculate to see the result and Formula & steps. Select Reset to clear the inputs and result.
Apply M = n / V
For Molarity (M), the calculator divides moles of solute by solution volume in liters. For Amount of solute (n), it uses n = M x V. For Volume of solution (V), it uses V = n / M.
Amount of solute: 0.5 mol
Volume of solution: 2 L
Molarity: 0.25 mol/L (M)When Amount of solute is a mass, the calculator first uses n = mass / molar mass. It needs the value in Molar mass of solute (g/mol); it does not derive molar mass from a chemical formula.
Units and input rules
- Amount of solute accepts
mol,mmol,µmol, g (mass), and mg (mass). - Volume of solution accepts Liters (L), Milliliters (mL), and Microliters (µL).
- Molarity accepts mol/L (M), mmol/L (mM), and µmol/L (µM).
Every required value must be a positive decimal number no larger than 1e12. The calculator rejects empty values, zero, negative values, non-numeric text, and scientific notation such as 1e-3. It also rejects a result that is infinite or zero.
Mass output has a missing input
Use mol, mmol, or µmol when Solve for is Amount of solute (n). When you choose g (mass) or mg (mass) as that output unit, the calculator hides Molar mass of solute (g/mol), so the mass conversion receives no molar mass and the displayed mass result is 0. Mass input works when solving for Molarity (M) or Volume of solution (V), provided you enter a positive molar mass.
Read, copy, or download the result
After Calculate, the result shows the selected quantity, normalized values, the formula, and each calculation step. A mass input adds a mass-to-moles step. Select Copy result for the generated text, or select Download result (.txt) to create molarity-calculator-result.txt. If copying fails, the page displays "Could not copy - select and copy manually."
The arithmetic runs in browser JavaScript. The calculator script does not submit the entered values to a server, and it does not look up density, compound properties, temperature effects, or dissolution behavior.
Use the calculation in a worksheet or preparation record
For a worksheet check, enter moles and solution volume, then compare the displayed formula and steps with your working. For a preparation record, enter a weighed mass, its molar mass, and the solution volume or target molarity.
Choose a related science calculator
Use Science Calculators to choose among chemistry, physics, electrical, optics, wave, fluid, gas, and radioactive-decay calculations. Use the Dilution Calculator for stock and target concentrations with C1V1 = C2V2. Use the Molar Mass Calculator when the missing value comes from a chemical formula. Use the Chemistry Calculator for pH, stoichiometry, and solution preparation calculations.
Frequently asked questions
How do I calculate molarity from moles and volume?
Enter Amount of solute and Volume of solution, choose Molarity (M) in Solve for, and select Calculate. The calculator converts the inputs to mol and liters, then applies M = n / V.
Can the molarity calculator use grams instead of moles?
Choose g (mass) or mg (mass) for Amount of solute and enter a positive Molar mass of solute (g/mol). The calculator converts that mass to moles before solving for Molarity (M) or Volume of solution (V).
Can I solve for volume or amount of solute?
Choose Volume of solution (V) or Amount of solute (n) in Solve for, then enter the other two known quantities. For an amount result, use mol, mmol, or µmol. The mass-output path hides Molar mass of solute (g/mol) and displays 0 for g (mass) or mg (mass).
What units does the molarity calculator support?
Amount of solute supports mol, mmol, µmol, g (mass), and mg (mass). Volume of solution supports Liters (L), Milliliters (mL), and Microliters (µL). Molarity supports mol/L (M), mmol/L (mM), and µmol/L (µM).
Does the calculator accept scientific notation?
It accepts decimal notation such as 0.001 and rejects entries such as 1e-3.