Concentration Converter

There are many ways to say how much solute is in a solution, and they catch everyone out. Describe one solution — how much solute, in how much water — and watch all four common measures appear at once. Change the amounts and see how each one responds.

Solute 10 g

Water (solvent) 90 g

Mass percent

% w/w

Mole fraction of solute

x₂

Molality

mol/kg

Molarity (approx.)

mol/L

Drag the two sliders to set the solution All four measures update together Watch which ones change with the amount of water

How each is worked out

The four measures

Mass %: mass of solute ÷ total mass × 100.
Mole fraction: moles of solute ÷ total moles.
Molality: moles of solute ÷ kilograms of solvent.
Molarity: moles of solute ÷ litres of solution.

Why molarity is the odd one

Mass %, mole fraction and molality use only masses, which do not change with temperature. Molarity uses the volume of the solution — and volume expands when warmed — so molarity is the one measure that changes with temperature. (This tool estimates volume assuming the solution is about as dense as water.)