Mole and mass converter

Converting mass and amount

Molar mass is the mass of one mole of a substance. Divide mass in grams by molar mass in g/mol to obtain the amount in moles. In the other direction, multiply amount by molar mass. A pure substance with a molar mass of 18.015 g/mol contains 2 mol in a 36.03 g sample.

Choosing the input

Use the molar mass for the correct chemical formula. Hydrated and anhydrous forms have different molar masses. The calculation does not correct for purity or reaction yield or derive an average molar mass for a mixture. Zero mass gives zero amount, but molar mass must be positive.

Choosing which mass is represented

The total weighed sample is not always the mass of the pure substance being calculated. For a solution, wet product or mixture, first determine the component mass. Entering solution volume in a gram field does not provide mass. This tool does not use composition or density to separate components.

For an arithmetic example, choose molar mass 50 g/mol and pure substance mass 60 g. Amount is 60/50 = 1.2 mol. In reverse, 1.2 × 50 = 60 g. The value 50 is an illustrative input, not a tabulated property of a named substance. Check the unit selector separately when entering mass in kg.

Molar mass is mass per mole, not the mass of one molecule or a solution concentration. A change in chemical formula changes the required molar mass. Do not treat a hydrated substance as its anhydrous form. Before using the amount in stoichiometry, identify the formula unit whose moles are being counted. Approximate mass and molar mass inputs also limit the result.

Frequently asked questions

How do you calculate moles from grams?

For an example pure sample of 36.03 g with molar mass 18.015 g/mol, dividing mass by molar mass gives an amount of 2 mol. Molar mass must correspond to the correct chemical formula, distinguishing hydrated and anhydrous substances, and this conversion excludes purity corrections and reaction yield.

Calculate with these values