The molar mass of silicon dioxide, SiO2, is 60.083 g/mol. That single number is what connects a mass you can weigh to an amount of substance you can react: one mole is 60.083 g, and a gram of it is 1.002e+22 formula units. The calculator turns any weighed mass into that count, and reports the amount in moles, millimoles and the mass of a single formula unit alongside it.
The figure comes from the formula. Silicon dioxide is 28.085 (Si) + 2 × 15.999 (O), which is 60.083 g/mol, taking standard atomic weights, and every page here computes that sum rather than quoting it. Oxygen makes up the largest share of the mass: 2 of the 3 atoms in a formula unit are oxygen, and they account for 31.998 g of the 60.083 g, or 53.26% by mass. The derivation table below breaks the whole molecule down element by element.
The numbers a bench actually uses sit at the millimole scale. One millimole of silicon dioxide is 60.083 mg and one micromole is 60.083 µg, so a balance reading to a milligram places you within 16.64 µmol. A single formula unit weighs 9.9770e-23 g, which is why the count in the gauge runs into the sextillions for any mass you can see.
Sand, quartz and glass. Also the anti-caking agent in powdered food, where it appears as silica. At 60.083 g/mol it is heavier than 1 of the 8 oxides covered here, and that ranking matters more than it looks: calcium oxide has a molar mass of 56.077 g/mol, so a gram of it contains 7.14% more formula units than a gram of silicon dioxide. Weigh by mass and you are not weighing equal amounts of substance.
Two practical things move the result. Purity below 100% means the weighed mass overstates how much compound you have — at 98% assay, 1.2017 g of every 60.083 g is not the compound — and any water picked up from the air does the same. Both are systematic, so they shift every solution made from that jar in the same direction.
The formula
m- The mass of silicon dioxide in grams
60.083- The molar mass of silicon dioxide in g/mol, derived from its formula
N- The number of formula units that mass contains
How it works, step by step
- Enter a mass of silicon dioxide in grams.
- It is divided by the molar mass, 60.083 g/mol, giving the amount in moles.
- That amount is multiplied by the Avogadro constant, 6.02214076 × 10²³ per mole, to give the number of formula units.
- The panel also reports the amount in moles and millimoles and the mass of one formula unit.
Worked examples
0.5 g of silicon dioxide as a molecule count
0.5 g divided by 60.083 g/mol is 0.00832182 mol, and multiplying by the Avogadro constant gives 5.012e+21 formula units of silicon dioxide. The same mass is 8.3218 mmol, which is the figure a reaction is actually planned in.
5 g of silicon dioxide as a molecule count
5 g divided by 60.083 g/mol is 0.0832182 mol, and multiplying by the Avogadro constant gives 5.012e+22 formula units of silicon dioxide. The same mass is 83.218 mmol, which is the figure a reaction is actually planned in.
50 g of silicon dioxide as a molecule count
50 g divided by 60.083 g/mol is 0.832182 mol, and multiplying by the Avogadro constant gives 5.012e+23 formula units of silicon dioxide. The same mass is 832.18 mmol, which is the figure a reaction is actually planned in.
How to read your score
Frequently asked questions
What is the molar mass of silicon dioxide (SiO2)?
It is 60.083 g/mol. That is the sum of the standard atomic weights of every atom in the formula: 28.085 (Si) + 2 × 15.999 (O). One mole of silicon dioxide therefore weighs 60.083 g, and a gram of it is 16.644 mmol.
What percentage of silicon dioxide is oxygen?
53.26% by mass. Each formula unit contains 2 oxygen atoms contributing 31.998 g of the 60.083 g total, so 100 g of silicon dioxide contains 53.26 g of oxygen and a kilogram contains 532.56 g of it.
How many molecules are in one gram of silicon dioxide?
About 1.002e+22. One gram is 0.0166436 mol, and each mole contains 6.02214076 × 10²³ formula units by definition of the mole, so the count is that constant divided by 60.083.
How much does a single molecule of silicon dioxide weigh?
9.9770e-23 g, which is 60.083 daltons. It is the molar mass divided by the Avogadro constant, and the number in daltons is numerically the same as the molar mass in g/mol — that equivalence is what makes the mole convenient.
Is molar mass the same as molecular weight?
They are the same number in ordinary use but not the same quantity. Molecular weight, properly relative molecular mass, is a ratio and has no unit: for silicon dioxide it is 60.083. Molar mass carries grams per mole: 60.083 g/mol. Because the mole is defined so those agree, you can read one off the other.
Why is the molar mass not a whole number?
Because standard atomic weights are averages over the isotopes found in nature. Oxygen is quoted as 15.999 rather than a whole number for that reason, and the same applies to the other elements here, which is why silicon dioxide comes out at 60.083 g/mol rather than 60.
Molar mass, composition and mole equivalents of silicon dioxide
| Element | Atoms | Atomic weight | Contribution (g/mol) | By mass |
|---|---|---|---|---|
| Oxygen (O) | 2 | 15.999 | 31.998 | 53.26% |
| Silicon (Si) | 1 | 28.085 | 28.085 | 46.74% |
| Total — one mole of silicon dioxide | 60.083 | 100% |
Standard atomic weights, IUPAC 2021. The contribution column is atoms × atomic weight, and the total is the molar mass this page uses: 60.083 g/mol.
| Amount | Mass (g) | Mass (mg) | Formula units |
|---|---|---|---|
| 1 µmol | 0.000060 | 0.060083 | 6.022e+17 |
| 10 µmol | 0.00060083 | 0.60083 | 6.022e+18 |
| 100 µmol | 0.0060083 | 6.0083 | 6.022e+19 |
| 1 mmol | 0.060083 | 60.083 | 6.022e+20 |
| 10 mmol | 0.60083 | 600.83 | 6.022e+21 |
| 50 mmol | 3.00415 | 3004.15 | 3.011e+22 |
| 100 mmol | 6.0083 | 6008.3 | 6.022e+22 |
| 250 mmol | 15.0207 | 15,020.8 | 1.506e+23 |
| 500 mmol | 30.0415 | 30,041.5 | 3.011e+23 |
| 750 mmol | 45.0622 | 45,062.2 | 4.517e+23 |
| 1 mol | 60.083 | 60,083 | 6.022e+23 |
| 2 mol | 120.166 | 120,166 | 1.204e+24 |
| 5 mol | 300.415 | 300,415 | 3.011e+24 |
| 10 mol | 600.83 | 600,830 | 6.022e+24 |
Mass is the amount multiplied by 60.083 g/mol. The last column is that amount multiplied by the Avogadro constant, 6.02214076 × 10²³ per mole.
| Compound | Formula | Molar mass (g/mol) | Millimoles in 1 g |
|---|---|---|---|
| Calcium oxide | CaO | 56.077 | 17.833 |
| Silicon dioxide (this page) | SiO2 | 60.083 | 16.644 |
| Copper(II) oxide | CuO | 79.545 | 12.572 |
| Titanium dioxide | TiO2 | 79.865 | 12.521 |
| Zinc oxide | ZnO | 81.379 | 12.288 |
| Manganese dioxide | MnO2 | 86.93604 | 11.503 |
| Aluminium oxide | Al2O3 | 101.9601 | 9.8078 |
Ordered by molar mass. The last column is 1000/M, which is the number a weighed gram actually gives you.