Calculate molarity, solute mass, molar mass or solution volume using M = m / (MW x V). Supports mol/L, mM, uM and mass concentration.
Use this molarity calculator to calculate solution concentration, solute mass, molar mass, or solution volume with the formula M = m / (MW x V). It fits common chemistry tasks such as solution preparation, dilution checks, buffer mixing, and converting between mol/L, mM, uM, and mass concentrations such as mg/mL and µg/mL.
Common workflows include finding how many grams are needed for a target molarity, converting mg/mL to molarity from molecular weight, or checking the final concentration after setting mass and volume.
The calculator also shows moles of solute and mass concentration, so it is useful when a lab protocol gives one format and you need the other. Reverse solving helps when you know the target molarity and final volume and need to find the required solute mass quickly.
Molarity formula
$$M=\frac{m}{MW\cdot V}$$
Frequently asked questions about molarity
What is molarity?
Molarity is the amount of solute in one liter of solution. It is written as mol/L or simply M, and it is one of the most common concentration units in chemistry and lab work.
What formula does the molarity calculator use?
The calculator uses M = m / (MW x V), where m is solute mass, MW is molar mass, and V is solution volume. The same relationship can be rearranged to solve for concentration, mass, molar mass, or volume.
How do I find the mass needed for a target molarity?
Enter the molar mass, target concentration, and final volume, and the calculator will return the required solute mass. This is the standard workflow when preparing stock solutions, buffers, and routine lab reagents.
What is the difference between molarity and molality?
Molarity is based on liters of solution, while molality is based on kilograms of solvent. Molarity is usually preferred for solution preparation, while molality is more useful when temperature-related volume changes matter.
Which units can I use?
You can work with common mass, volume, and concentration units such as g, mg, L, mL, M, mM, and uM. The calculator also shows mass concentration and moles, which helps when a protocol mixes concentration formats.
How do I convert mg/mL to molarity?
Divide the mass concentration by the molar mass. Because mg/mL equals g/L, the molarity is M (mol/L) = (mg/mL) / MW. Enter the mass, molar mass, and volume — or read the mass-concentration output directly — and the calculator returns molarity in mol/L, mM, and uM.
How do I convert µg/mL to molarity?
Use the same relationship — molarity equals mass concentration divided by molar mass — keeping the units consistent. A µg/mL value is common for drugs, antibodies, and dilute reagents; enter it and the calculator scales the result into mol/L, mM, and uM so you can use the format your protocol needs.
How do I convert a concentration or percent solution to molarity?
First express the concentration as a mass concentration such as g/L or mg/mL: a % w/v solution is grams of solute per 100 mL, so 1% = 10 g/L. Then divide by the molar mass to get molarity. The calculator performs this step once you enter the mass, molar mass, and volume.
