Four calculators, one panel.
Pick a mode below — mix and match units freely, everything recalculates live as you type, and every result explains itself.
The weight of the sample you're measuring.
Add up the atomic masses in the formula, or look it up on the periodic table.
The known amount of substance.
Must be greater than zero to solve for mass.
The known mass of the sample.
Must be greater than zero to solve for molar mass.
The amount of substance dissolved.
Must be greater than zero to calculate molarity.
Two inputs to an answer.
No manual required — but here's the entire flow in four moves.
Pick a mode
Moles from mass for a mass you already measured. Solve mass or Solve molar mass for the two reverse cases. Molarity for solution concentration.
Enter what you know
Type a number and pick its unit from the dropdown next to it — grams, pounds, litres or millilitres all convert automatically. The example chips fill everything in with one tap.
Read the results
The main answer sits up top in large type. Related values in other units sit below, and the exact formula with your numbers substituted sits at the bottom.
Trust the checks
Impossible inputs — negative mass, a zero molar mass or volume you're trying to divide by — get flagged with a plain-English reason instead of a wrong or broken answer. Copy any result set with one click.
One relationship, four ways to use it.
Every mode above comes from the same handful of equations, just solved for a different letter.
Moles from mass
Mass in grams divided by molar mass in g/mol gives the amount of substance in moles.
Mass from moles
Multiply the number of moles by the molar mass to get the mass in grams.
Molar mass
Divide the mass of a sample by the number of moles it contains.
Molarity
Moles of solute divided by litres of solution gives the concentration in mol/L.
Questions people actually ask.
The short answers — with the long ones one tap away.
What is a mole in chemistry?+
A mole is the SI unit for amount of substance. One mole of anything contains exactly 6.02214076 × 10²³ particles (Avogadro's number) — atoms, molecules, ions, or formula units. It's the bridge between the microscopic world of atoms and the measurable, weighable world of grams.
How do I calculate moles from grams?+
Divide the mass by the molar mass: n = m ÷ M. For example, 18 g of water divided by its molar mass of 18.02 g/mol gives almost exactly 1 mole. Enter both values in the Moles from mass tab to get the answer instantly, along with the particle count.
How do I find molar mass?+
Molar mass is mass divided by moles: M = m ÷ n. If you know how many grams and how many moles a sample contains, the Solve molar mass tab rearranges the formula for you. It can also be found by adding up the atomic masses in a chemical formula.
How do I calculate molarity?+
Molarity is moles of solute divided by litres of solution: C = n ÷ V. Enter the moles and the solution volume in the Molarity tab and it returns the concentration in mol/L (M), along with mmol/L and µmol/L.
How many particles are in a mole?+
Exactly 6.02214076 × 10²³ particles, known as Avogadro's number. This holds regardless of the substance — one mole of carbon atoms and one mole of water molecules both contain the same number of particles, just with very different total masses.
What is the molar volume of a gas at STP?+
At standard temperature and pressure (0°C and 1 atm), one mole of any ideal gas occupies 22.414 L. The Moles from mass tab shows this figure automatically so you can see what volume a gas sample would occupy at STP.
Is this tool free, and where does my data go?+
It's completely free and runs entirely in your browser — nothing you type is uploaded, logged, or sent to any server. No account, no sign-up, no limits.