The molar mass of glucose, C6H12O6, is 180.156 g/mol. That single number is what connects a mass you can weigh to an amount of substance you can react: one mole is 180.156 g, and a gram of it is 3.343e+21 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. Glucose is 6 × 12.011 (C) + 12 × 1.008 (H) + 6 × 15.999 (O), which is 180.156 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: 6 of the 24 atoms in a formula unit are oxygen, and they account for 95.994 g of the 180.156 g, or 53.28% 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 glucose is 180.156 mg and one micromole is 180.156 µg, so a balance reading to a milligram places you within 5.551 µmol. A single formula unit weighs 2.9916e-22 g, which is why the count in the gauge runs into the sextillions for any mass you can see.
Blood sugar, dextrose in the kitchen and the standard carbon source in microbiology. Labs report it in mg/dL in the US and mmol/L elsewhere. At 180.156 g/mol it is heavier than 15 of the 21 organic compounds covered here, and that ranking matters more than it looks: uric acid has a molar mass of 168.112 g/mol, so a gram of it contains 7.16% more formula units than a gram of glucose. 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, 3.6031 g of every 180.156 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 glucose in grams
180.156- The molar mass of glucose 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 glucose in grams.
- It is divided by the molar mass, 180.156 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 glucose as a molecule count
0.5 g divided by 180.156 g/mol is 0.00277537 mol, and multiplying by the Avogadro constant gives 1.671e+21 formula units of glucose. The same mass is 2.7754 mmol, which is the figure a reaction is actually planned in.
5 g of glucose as a molecule count
5 g divided by 180.156 g/mol is 0.0277537 mol, and multiplying by the Avogadro constant gives 1.671e+22 formula units of glucose. The same mass is 27.754 mmol, which is the figure a reaction is actually planned in.
50 g of glucose as a molecule count
50 g divided by 180.156 g/mol is 0.277537 mol, and multiplying by the Avogadro constant gives 1.671e+23 formula units of glucose. The same mass is 277.54 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 glucose (C6H12O6)?
It is 180.156 g/mol. That is the sum of the standard atomic weights of every atom in the formula: 6 × 12.011 (C) + 12 × 1.008 (H) + 6 × 15.999 (O). One mole of glucose therefore weighs 180.156 g, and a gram of it is 5.5507 mmol.
What percentage of glucose is oxygen?
53.28% by mass. Each formula unit contains 6 oxygen atoms contributing 95.994 g of the 180.156 g total, so 100 g of glucose contains 53.28 g of oxygen and a kilogram contains 532.84 g of it.
How many molecules are in one gram of glucose?
About 3.343e+21. One gram is 0.00555074 mol, and each mole contains 6.02214076 × 10²³ formula units by definition of the mole, so the count is that constant divided by 180.156.
How much does a single molecule of glucose weigh?
2.9916e-22 g, which is 180.156 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 glucose it is 180.156. Molar mass carries grams per mole: 180.156 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 glucose comes out at 180.156 g/mol rather than 180.
Molar mass, composition and mole equivalents of glucose
| Element | Atoms | Atomic weight | Contribution (g/mol) | By mass |
|---|---|---|---|---|
| Oxygen (O) | 6 | 15.999 | 95.994 | 53.28% |
| Carbon (C) | 6 | 12.011 | 72.066 | 40% |
| Hydrogen (H) | 12 | 1.008 | 12.096 | 6.714% |
| Total — one mole of glucose | 180.156 | 100% |
Standard atomic weights, IUPAC 2021. The contribution column is atoms × atomic weight, and the total is the molar mass this page uses: 180.156 g/mol.
| Amount | Mass (g) | Mass (mg) | Formula units |
|---|---|---|---|
| 1 µmol | 0.000180156 | 0.180156 | 6.022e+17 |
| 10 µmol | 0.00180156 | 1.80156 | 6.022e+18 |
| 100 µmol | 0.0180156 | 18.0156 | 6.022e+19 |
| 1 mmol | 0.180156 | 180.156 | 6.022e+20 |
| 10 mmol | 1.80156 | 1801.56 | 6.022e+21 |
| 50 mmol | 9.0078 | 9007.8 | 3.011e+22 |
| 100 mmol | 18.0156 | 18,015.6 | 6.022e+22 |
| 250 mmol | 45.039 | 45,039 | 1.506e+23 |
| 500 mmol | 90.078 | 90,078 | 3.011e+23 |
| 750 mmol | 135.117 | 135,117 | 4.517e+23 |
| 1 mol | 180.156 | 180,156 | 6.022e+23 |
| 2 mol | 360.312 | 360,312 | 1.204e+24 |
| 5 mol | 900.78 | 900,780 | 3.011e+24 |
| 10 mol | 1801.56 | 1801560.000000 | 6.022e+24 |
Mass is the amount multiplied by 180.156 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 |
|---|---|---|---|
| Tris base | C4H11NO3 | 121.136 | 8.2552 |
| Paracetamol | C8H9NO2 | 151.165 | 6.6153 |
| Uric acid | C5H4N4O3 | 168.112 | 5.9484 |
| Glucose (this page) | C6H12O6 | 180.156 | 5.5507 |
| Aspirin | C9H8O4 | 180.159 | 5.5507 |
| Caffeine | C8H10N4O2 | 194.194 | 5.1495 |
| EDTA | C10H16N2O8 | 292.244 | 3.4218 |
Ordered by molar mass. The last column is 1000/M, which is the number a weighed gram actually gives you.