Moles to grams for sucrose is a multiplication by 342.297 g/mol. A mole weighs 342.297 g, 100 mmol weighs 34.2297 g, 10 mmol weighs 3.42297 g and a millimole is 342.297 mg. Those four figures cover most of what gets weighed out in practice, and the table below extends them from a micromole up to ten moles.
The figure comes from the formula. Sucrose is 12 × 12.011 (C) + 22 × 1.008 (H) + 11 × 15.999 (O), which is 342.297 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: 11 of the 45 atoms in a formula unit are oxygen, and they account for 175.989 g of the 342.297 g, or 51.41% by mass. The derivation table below breaks the whole molecule down element by element.
Two habits make the weighed mass match the calculation. Weigh into a container you have tared rather than onto paper, because what stays behind on paper is a real loss — on a 100 mg weighing it is easily a percent. And when the target is under about 20 mg, weigh ten times that and dilute, since the absolute error of the balance does not shrink with the sample.
Table sugar, a disaccharide of glucose and fructose. Sugar solutions are quoted in degrees Brix, which is percent by weight rather than molarity. At 342.297 g/mol it is heavier than 19 of the 21 organic compounds covered here, and that ranking matters more than it looks: EDTA has a molar mass of 292.244 g/mol, so a gram of it contains 17.1% more formula units than a gram of sucrose. Weigh by mass and you are not weighing equal amounts of substance.
Purity is the usual gap between the calculation and the balance. A reagent sold at 98% means 6.8459 g of a nominal 342.297 g is something else, so for exact work you divide the weighed mass by the assay figure on the certificate. For most purposes the difference is smaller than the error in reading the meniscus, but it is systematic rather than random, so it does not average out.
The formula
n- The amount of sucrose you need, in moles
342.297- The molar mass of sucrose in g/mol, derived from its formula
m- The mass to weigh out, in grams
How it works, step by step
- Enter the amount you need, in moles.
- It is multiplied by 342.297 g/mol.
- The result is the mass to weigh out, also given in milligrams.
- Weigh into a tared container; anything left in the boat is a real loss from the amount you calculated.
Worked examples
5 mmol of sucrose in grams
5 mmol × 342.297 g/mol = 1.71149 g, which is 1711.49 mg. Doubling the amount doubles the mass to 3.42297 g, because the relationship is a plain proportion once the molar mass is fixed.
250 mmol of sucrose in grams
250 mmol × 342.297 g/mol = 85.5743 g, which is 85,574.2 mg. Doubling the amount doubles the mass to 171.149 g, because the relationship is a plain proportion once the molar mass is fixed.
2 mol of sucrose in grams
2 mol × 342.297 g/mol = 684.594 g, which is 684,594 mg. Doubling the amount doubles the mass to 1369.19 g, because the relationship is a plain proportion once the molar mass is fixed.
How to read your score
Frequently asked questions
What is the molar mass of sucrose (C12H22O11)?
It is 342.297 g/mol. That is the sum of the standard atomic weights of every atom in the formula: 12 × 12.011 (C) + 22 × 1.008 (H) + 11 × 15.999 (O). One mole of sucrose therefore weighs 342.297 g, and a gram of it is 2.9214 mmol.
What percentage of sucrose is oxygen?
51.41% by mass. Each formula unit contains 11 oxygen atoms contributing 175.989 g of the 342.297 g total, so 100 g of sucrose contains 51.41 g of oxygen and a kilogram contains 514.14 g of it.
How many grams is one mole of sucrose?
342.297 g, by definition of the molar mass. Two moles is 684.594 g and half a mole is 171.1485 g.
How many grams is 0.1 mol, and how many milligrams is 1 mmol?
0.1 mol of sucrose is 34.2297 g. One millimole is 342.297 mg and one micromole is 342.297 µg, which is the range most bench work sits in.
How do I weigh out an amount too small for my balance?
Weigh a larger mass and dilute it. To get 3.423 mg of sucrose, weigh 34.23 mg into 100 mL, then take 10 mL of that: the absolute error of the balance stays the same while the amount delivered falls by a factor of ten.
Should I use the hydrate or the anhydrous molar mass?
This page is the anhydrous form, C12H22O11, at 342.297 g/mol. If your jar is the other form the molar mass differs and so will every mass you weigh, so check the label before using the figure. Salts that are sold as hydrates weigh more per mole because the water is part of the crystal.
Moles to grams reference for sucrose
| Element | Atoms | Atomic weight | Contribution (g/mol) | By mass |
|---|---|---|---|---|
| Oxygen (O) | 11 | 15.999 | 175.989 | 51.41% |
| Carbon (C) | 12 | 12.011 | 144.132 | 42.11% |
| Hydrogen (H) | 22 | 1.008 | 22.176 | 6.479% |
| Total — one mole of sucrose | 342.297 | 100% |
Standard atomic weights, IUPAC 2021. The contribution column is atoms × atomic weight, and the total is the molar mass this page uses: 342.297 g/mol.
| Wanted | Weigh (g) | Weigh (mg) | With 2% over (g) |
|---|---|---|---|
| 1 µmol | 0.000342297 | 0.342297 | 0.000349143 |
| 10 µmol | 0.00342297 | 3.42297 | 0.00349143 |
| 100 µmol | 0.0342297 | 34.2297 | 0.0349143 |
| 1 mmol | 0.342297 | 342.297 | 0.349143 |
| 10 mmol | 3.42297 | 3422.97 | 3.49143 |
| 50 mmol | 17.1149 | 17,114.9 | 17.4571 |
| 100 mmol | 34.2297 | 34,229.7 | 34.9143 |
| 250 mmol | 85.5743 | 85,574.2 | 87.2857 |
| 500 mmol | 171.149 | 171,148 | 174.571 |
| 750 mmol | 256.723 | 256,723 | 261.857 |
| 1 mol | 342.297 | 342,297 | 349.143 |
| 2 mol | 684.594 | 684,594 | 698.286 |
| 5 mol | 1711.49 | 1711485.000000 | 1745.71 |
| 10 mol | 3422.97 | 3422970.000000 | 3491.43 |
Weigh is the amount multiplied by 342.297 g/mol. The last column carries a 2% allowance, which is what you take when some of the solid will be left in the weighing boat.
| Compound | Formula | Molar mass (g/mol) | Millimoles in 1 g |
|---|---|---|---|
| Uric acid | C5H4N4O3 | 168.112 | 5.9484 |
| Glucose | C6H12O6 | 180.156 | 5.5507 |
| Aspirin | C9H8O4 | 180.159 | 5.5507 |
| Caffeine | C8H10N4O2 | 194.194 | 5.1495 |
| EDTA | C10H16N2O8 | 292.244 | 3.4218 |
| Sucrose (this page) | C12H22O11 | 342.297 | 2.9214 |
| Cholesterol | C27H46O | 386.664 | 2.5862 |
Ordered by molar mass. The last column is 1000/M, which is the number a weighed gram actually gives you.