Molarity calculator explained
The molarity calculator links sample mass, molar mass, and solution volume so you can answer any concentration question without reworking the algebra. It is ideal when you need to know how many grams of reagent deliver a target molarity, or when you are double-checking whether a reported molarity matches the mass and volume written in a notebook.
Enter whichever values you have: {mass}, {molar_mass}, {volume}, or {molarity}, and the calculator solves for the missing quantity. That keeps lab prep moving because you focus on stocking flasks instead of juggling unit conversions.
How the conversion works
Molarity measures moles of solute per liter of solution:
where is moles, is mass, is molar mass, and is volume in liters. Multiplying molarity by molar mass gives mass concentration in g/L, which is why the calculator exposes the {concentration} field alongside molarity.
Units and conversions
| Quantity | Symbol | Recommended units | Notes |
|---|---|---|---|
| Molarity | mol/L | Convert from mmol/L by dividing by . | |
| Mass | g | 1 mg = g. | |
| Molar mass | g/mol | Pull from SDS or sum atomic weights. | |
| Volume | L | Divide mL by to get liters. | |
| Mass concentration | g/L | . |
Always convert volume to liters before dividing; otherwise the molarity will be off by powers of ten.
Worked examples
- Converting grams to molarity
Dissolve of NaCl () in .
Report the solution as NaCl; the calculator simultaneously shows .
- How many grams for a target molarity
Need (0.250 L) of a KCl solution. KCl has .
Weigh 28.0 g to the nearest tenth and dilute to the mark to hit the target molarity.
Tips and pitfalls
- Always measure volume after the solute dissolves; filling to the mark first introduces error.
- Use temperature-corrected volumetric glassware when preparing concentrated acids because thermal expansion changes volume.
- If density is known instead of volume, convert to volume (L) before applying the formula.
- Double-check molar mass for hydrates; e.g., CuSO5HO has 5 extra water molecules that change significantly.