Going from grams to moles for sucrose means dividing by its molar mass, 342.297 g/mol. One gram is 0.00292144 mol, or 2.92144 mmol; 100 mg is 0.29214 mmol; and a 342.297 g portion is exactly one mole. The division is the whole calculation, but the molar mass has to be the one for the exact formula you have, C12H22O11, which is where these figures come from.
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.
Balance resolution is the practical limit here. On a two-decimal balance the smallest step is 10 mg, which is 0.02921 mmol of sucrose; on a three-decimal balance it is 1 mg, or 2.921 µmol. To hit a target within 1% you therefore need to weigh at least a gram on the first and at least 100 mg on the second, and below that a stock solution measured by pipette beats weighing.
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.
Two practical things move the result. Purity below 100% means the weighed mass overstates how much compound you have — at 98% assay, 6.8459 g of every 342.297 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 you weighed, in grams
342.297- The molar mass of sucrose in g/mol, derived from its formula
n- The amount of substance in moles
How it works, step by step
- Enter the mass you weighed, in grams.
- It is divided by 342.297 g/mol, the molar mass of sucrose.
- The result is the amount of substance in moles, with millimoles and micromoles beneath it.
- Check it against the table if you want the figure for a standard weighing rather than a typed mass.
Worked examples
0.25 g of sucrose in moles
0.25 ÷ 342.297 = 0.00073036 mol, or 0.73036 mmol. If the balance was reading to 1 mg, the last digit of that mass is worth 2.921 µmol, so quoting the answer to more than four significant figures claims a precision the weighing did not have.
2 g of sucrose in moles
2 ÷ 342.297 = 0.00584288 mol, or 5.8429 mmol. If the balance was reading to 1 mg, the last digit of that mass is worth 2.921 µmol, so quoting the answer to more than four significant figures claims a precision the weighing did not have.
25 g of sucrose in moles
25 ÷ 342.297 = 0.073036 mol, or 73.036 mmol. If the balance was reading to 1 mg, the last digit of that mass is worth 2.921 µmol, so quoting the answer to more than four significant figures claims a precision the weighing did not have.
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 do I convert grams of sucrose to moles?
Divide the mass in grams by 342.297 g/mol. So 1 g is 0.00292144 mol, 10 g is 0.0292144 mol and 100 g is 0.292144 mol. Nothing else enters the calculation — no volume, no temperature, no concentration.
How many moles is 100 g of sucrose?
0.292144 mol, which is 292.144 mmol. Read the other way, one mole of sucrose is 342.297 g, so 100 g is 0.2921 of a mole.
What about milligrams and micromoles?
The same division, scaled. A milligram of sucrose is 2.9214 µmol, 10 mg is 29.214 µmol and 100 mg is 0.29214 mmol. Working in µmol per mg avoids the string of leading zeros that mol per g produces at this scale.
Does purity change the number of moles?
Yes, in proportion. A 98% pure sample weighing 1 g contains 0.98 g of sucrose, which is 0.00286301 mol rather than 0.00292144 mol. The calculator assumes the mass you enter is the compound itself, so divide by the assay figure first if you need the corrected amount.
Grams to moles 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.
| On the balance | Moles | Millimoles | Micromoles |
|---|---|---|---|
| 1 mg | 0.000003 | 0.00292144 | 2.92144 |
| 5 mg | 0.000015 | 0.0146072 | 14.6072 |
| 10 mg | 0.000029 | 0.0292144 | 29.2144 |
| 25 mg | 0.000073 | 0.073036 | 73.036 |
| 50 mg | 0.000146072 | 0.146072 | 146.072 |
| 100 mg | 0.000292144 | 0.292144 | 292.144 |
| 250 mg | 0.00073036 | 0.73036 | 730.36 |
| 500 mg | 0.00146072 | 1.46072 | 1460.72 |
| 1 g | 0.00292144 | 2.92144 | 2921.44 |
| 2 g | 0.00584288 | 5.84288 | 5842.88 |
| 5 g | 0.0146072 | 14.6072 | 14,607.2 |
| 10 g | 0.0292144 | 29.2144 | 29,214.4 |
| 25 g | 0.073036 | 73.036 | 73,036 |
| 50 g | 0.146072 | 146.072 | 146,072 |
| 100 g | 0.292144 | 292.144 | 292,144 |
| 250 g | 0.73036 | 730.36 | 730,360 |
| 500 g | 1.46072 | 1460.72 | 1460719.784281 |
Every row is the mass divided by 342.297 g/mol. A balance reading to 1 mg resolves 2.921 µmol of this compound, which is the smallest step the middle columns can really move in.
| 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.