Online calculator: Convert grams to moles and moles to grams

In many chemistry problems, you need to convert grams to moles or moles to grams.

The calculator below calculates the mass of the substance in grams or the quantity of the substance in moles. Depending on the input data it can serve either as grams to moles calculator or as moles to grams calculator. It also displays the molar mass of the chemical substance and details of its calculation just for reference. You can find more information and formulas about grams to moles conversion as well as about moles to grams conversion below the calculator.

Note: Always use the upper case for the first character in the element name and the lower case for the second character as in the periodic table. Compare: Co - cobalt and CO - carbon monoxide. Thus, Na3PO4 — correct notation, na3po4/NA3PO4 — incorrect notation.

Convert moles to grams and grams to moles.

Substance formula

Convert

grams to moles

moles to grams

Mass of the substance, grams

Quantity of the substance, moles

Calculation precision

Digits after the decimal point: 3

Mass of the substance, grams

Quantity of the substance, moles

Molar mass of the substance

Molar mass details

Conversion formula

There is a simple relation between grams and moles:
$\frac{m_s}{N_s}=M_s$ ,
where
$m_s$ - mass of the substance in grams
$N_s$ - quantity of the substance in moles
$M_s$ - molar mass of the substance in grams/mole

How to convert grams to moles?

You need to divide the mass of the substance by the molar mass of the substance:
$N_s=\frac{m_s}{M_s}$

How to convert moles to grams?

You need to multiply the molar mass of the substance by the number of moles:
$m_s=M_s \cdot N_s$

As you can see, the most difficult task here is finding out the molar mass of the substance.

The molar mass of the substance

The molar mass is a physical property defined as the mass of a given substance (chemical element or chemical compound) divided by the amount of substance. The molar mass of atoms of an element is given by the standard relative atomic mass of the element multiplied by the molar mass constant, 1 × 10−3 kg/mol = 1 g/mol. The molar mass of a compound is given by the sum of the standard atomic weight (namely, the standard relative atomic mass) of the atoms which form the compound multiplied by the molar mass constant. Multiplying by the molar mass constant ensures that the calculation is dimensionally correct: standard relative atomic masses are dimensionless quantities (i.e., pure numbers), whereas molar masses have units (in this case, grams/mole).

And this is where our grams to moles/moles to grams calculator shines, thanks to our other calculator - Molar mass of the substance, which calculates molar mass for a substance given the formula.

All you need to do is correctly enter your formula, choose whether you want a conversion from grams to moles or a conversion from moles to grams, and, in case of g to mol, enter the mass, or, in case of mol to g, enter the moles.

Grams to moles example problem

Problem: Convert 25.0 grams of KMnO4 to moles.
Solution:

Find out the molar mass of the substance (hint: you can use Molar mass of the substance alone to calculate molar mass).
The molar mass of KMnO4 is 158.032 g/mol.
Divide the given mass (25.0 g) by the molar mass (158.032 g/mol) to get the moles.
The number of moles of KMnO4 will be 0.158

And here is how you should enter this problem into the calculator above: grams to moles problem solution

Moles to grams example problem

Problem: Convert 2.50 moles of KClO3 to grams.
Solution:

Find out the molar mass of the substance (hint: you can use Molar mass of the substance alone to calculate molar mass).
The molar mass of KClO3 is 122.548 g/mol.
Multiply the given number of moles (2.50 mol) by the molar mass (122.548 g/mol) to get the grams.
The number of grams of KClO3 will be 306.37

And here is how you should enter this problem into the calculator above: moles to grams problem solution

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Convert grams to moles and moles to grams