Transparent method
The formula
Worked example
Example inputs
How to interpret the result
Molarity is defined against a specific solution volume, and because liquids expand and contract with temperature, the identical mass of dissolved solute in the identical container can measure as a slightly different molarity depending on the temperature at which the volume was measured, a real effect, not a calculation error.
Before you rely on it
What to check
Note the temperature at which a solution's volume was measured when precision matters, since molarity is technically temperature-dependent even though the mass of solute hasn't changed.
The common error
Where people go wrong with molarity calculator
Treating molarity as a temperature-independent fixed property of a solution. The volume it's calculated against shifts slightly with temperature, so precise work needs to account for that rather than assuming the figure holds at any temperature.
Sensitivity evidence
How moles of solute changes the molarity (mol/l)
| Moles of solute | Molarity (mol/L) | Millimolar (mmol/L) |
|---|---|---|
| 0.4 | 0.4 | 400 |
| 0.45 | 0.45 | 450 |
| 0.5worked example | 0.5 | 500 |
| 0.55 | 0.55 | 550 |
| 0.6 | 0.6 | 600 |
Every input, tested
Which input moves the molarity (mol/l) most
| Input | Tested from | To | Molarity (mol/L) at each end | Swing |
|---|---|---|---|---|
| Solution volume (L) | 0.9 | 1.1 | 0.556 to 0.455 | 0.101 (20%) |
| Moles of solute | 0.45 | 0.55 | 0.45 to 0.55 | 0.1 (20%) |
Two variables at once
Molarity (mol/L) by moles of solute and solution volume (l)
| Moles of solute \ Solution volume (L) | 0.8 | 1 | 1.2 |
|---|---|---|---|
| 0.4 | 0.5 | 0.4 | 0.333 |
| 0.45 | 0.563 | 0.45 | 0.375 |
| 0.5 | 0.625 | 0.5 | 0.417 |
| 0.55 | 0.688 | 0.55 | 0.458 |
| 0.6 | 0.75 | 0.6 | 0.5 |
Step by step
The worked example, input by input
| Input | Value used |
|---|---|
| Moles of solute | 0.5 |
| Solution volume (L) | 1 |
| Molarity (mol/L) | 0.5 |
| Millimolar (mmol/L) | 500 |
Where the inputs come from
Enter the moles of solute and the volume of the solution in liters. Moles are the mass of the substance divided by its molar mass, which you can find from the periodic table. The volume is the total volume of the final solution, not the volume of solvent added. If you have milliliters, divide by 1,000. Use a volumetric flask for accurate preparation.
When the result stops applying
The formula assumes complete dissolution. For strong acids and bases, molarity of the solution differs from the concentration of ions, and weak acids only partly ionize. Always follow safety rules when handling chemicals.
What to compare it with
Prepare dilutions on the dilution calculator, express concentrations as parts per million on the ppm page, find pH on the pH calculator and mass on the weight converter. The density and percent yield calculators are used in the same laboratory work.
People also ask
Frequently asked questions
What does molarity measure exactly?
The number of moles of solute dissolved per liter of solution, written as mol/L or M.
How do I find moles from grams?
Divide the mass in grams by the molar mass of the substance, from the periodic table.
Why use the volume of the solution and not the solvent?
Because dissolving the solute changes the total volume, and molarity is defined per liter of the final solution.