Mole Calculator: Mass to Moles
Convert sample mass to moles using its molar mass. Choose grams, milligrams or kilograms and see the amount in mol and mmol with clear unit conversions.
Convert a measured sample mass into an amount of substance when its molar mass is known. This is the mass-to-moles step used before comparing reaction quantities or preparing a solution. The result refers to the substance represented by the molar mass you enter.
How to use this tool
- Enter the sample mass and select g, mg or kg.
- Enter the molar mass in g/mol for the correct chemical form.
- Read the amount in mol and the equivalent amount in mmol.
- Check the converted gram value before using the result in another calculation.
Formula
n = m / M; 1 mg = 0.001 g; 1 kg = 1000 g
n is amount in mol, m is mass in grams, and M is molar mass in g/mol. M must be positive. Zero sample mass gives zero moles; negative mass is rejected.
Example
For a sample with mass 36.03 g and molar mass 18.015 g/mol, divide 36.03 by 18.015. The result is 2 mol, or 2000 mmol. Entering 0.03603 kg produces the same answer.
Frequently asked questions
Where do I find molar mass?
Use a reliable chemical specification or calculate it from the complete formula. Include waters of hydration when they are part of the material. Relative molecular mass is dimensionless; this input requires a value expressed in g/mol.
Can I use the total mass of a solution?
Only if it is the mass of the substance whose moles you want. For a solution or impure sample, first determine the relevant component mass from its composition. This tool does not assume a purity percentage.
Does zero mass mean the molar mass can be zero?
No. Molar mass remains a positive material property even when the sample amount is zero. A zero denominator cannot define this conversion.
Why is a result written with e?
Scientific notation keeps very small amounts visible. For example, 1e-9 means one billionth. Arithmetic uses the entered values; displayed digits do not establish experimental accuracy.
Sources
Last updated: 2026-10-30