Going from grams to moles for sodium chloride means dividing by its molar mass, 58.439769 g/mol. One gram is 0.0171116 mol, or 17.1116 mmol; 100 mg is 1.7112 mmol; and a 58.43977 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, NaCl, which is where these figures come from.
The figure comes from the formula. Sodium chloride is 22.9898 (Na) + 35.45 (Cl), which is 58.439769 g/mol, taking standard atomic weights, and every page here computes that sum rather than quoting it. Chlorine makes up the largest share of the mass: 1 of the 2 atoms in a formula unit is chlorine, and they account for 35.45 g of the 58.43977 g, or 60.66% 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 0.1711 mmol of sodium chloride; on a three-decimal balance it is 1 mg, or 17.11 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 salt, and the solute in saline. A 0.9% w/v solution is isotonic with blood, which is the one concentration worth memorising. At 58.43977 g/mol it is heavier than 1 of the 34 salts covered here, and that ranking matters more than it looks: ammonium chloride has a molar mass of 53.489 g/mol, so a gram of it contains 9.26% more formula units than a gram of sodium chloride. 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, 1.1688 g of every 58.43977 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
58.439769- The molar mass of sodium chloride 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 58.439769 g/mol, the molar mass of sodium chloride.
- 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 sodium chloride in moles
0.25 ÷ 58.43977 = 0.00427791 mol, or 4.2779 mmol. If the balance was reading to 1 mg, the last digit of that mass is worth 17.11 µmol, so quoting the answer to more than four significant figures claims a precision the weighing did not have.
2 g of sodium chloride in moles
2 ÷ 58.43977 = 0.0342233 mol, or 34.223 mmol. If the balance was reading to 1 mg, the last digit of that mass is worth 17.11 µmol, so quoting the answer to more than four significant figures claims a precision the weighing did not have.
25 g of sodium chloride in moles
25 ÷ 58.43977 = 0.427791 mol, or 427.79 mmol. If the balance was reading to 1 mg, the last digit of that mass is worth 17.11 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 sodium chloride (NaCl)?
It is 58.439769 g/mol. That is the sum of the standard atomic weights of every atom in the formula: 22.9898 (Na) + 35.45 (Cl). One mole of sodium chloride therefore weighs 58.43977 g, and a gram of it is 17.112 mmol.
What percentage of sodium chloride is chlorine?
60.66% by mass. Each formula unit contains 1 chlorine atom contributing 35.45 g of the 58.43977 g total, so 100 g of sodium chloride contains 60.66 g of chlorine and a kilogram contains 606.61 g of it.
How do I convert grams of sodium chloride to moles?
Divide the mass in grams by 58.439769 g/mol. So 1 g is 0.0171116 mol, 10 g is 0.171116 mol and 100 g is 1.71116 mol. Nothing else enters the calculation — no volume, no temperature, no concentration.
How many moles is 100 g of sodium chloride?
1.71116 mol, which is 1711.16 mmol. Read the other way, one mole of sodium chloride is 58.43977 g, so 100 g is 1.711 of a mole.
What about milligrams and micromoles?
The same division, scaled. A milligram of sodium chloride is 17.112 µmol, 10 mg is 171.12 µmol and 100 mg is 1.7112 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 sodium chloride, which is 0.0167694 mol rather than 0.0171116 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 sodium chloride
| Element | Atoms | Atomic weight | Contribution (g/mol) | By mass |
|---|---|---|---|---|
| Chlorine (Cl) | 1 | 35.45 | 35.45 | 60.66% |
| Sodium (Na) | 1 | 22.98977 | 22.98977 | 39.34% |
| Total — one mole of sodium chloride | 58.439769 | 100% |
Standard atomic weights, IUPAC 2021. The contribution column is atoms × atomic weight, and the total is the molar mass this page uses: 58.439769 g/mol.
| On the balance | Moles | Millimoles | Micromoles |
|---|---|---|---|
| 1 mg | 0.000017 | 0.0171116 | 17.1116 |
| 5 mg | 0.000086 | 0.0855582 | 85.5582 |
| 10 mg | 0.000171116 | 0.171116 | 171.116 |
| 25 mg | 0.000427791 | 0.427791 | 427.791 |
| 50 mg | 0.000855582 | 0.855582 | 855.582 |
| 100 mg | 0.00171116 | 1.71116 | 1711.16 |
| 250 mg | 0.00427791 | 4.27791 | 4277.91 |
| 500 mg | 0.00855582 | 8.55582 | 8555.82 |
| 1 g | 0.0171116 | 17.1116 | 17,111.6 |
| 2 g | 0.0342233 | 34.2233 | 34,223.3 |
| 5 g | 0.0855582 | 85.5582 | 85,558.2 |
| 10 g | 0.171116 | 171.116 | 171,116 |
| 25 g | 0.427791 | 427.791 | 427,791 |
| 50 g | 0.855582 | 855.582 | 855,582 |
| 100 g | 1.71116 | 1711.16 | 1711163.497598 |
| 250 g | 4.27791 | 4277.91 | 4277908.743996 |
| 500 g | 8.55582 | 8555.82 | 8555817.487991 |
Every row is the mass divided by 58.439769 g/mol. A balance reading to 1 mg resolves 17.11 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 |
|---|---|---|---|
| Ammonium chloride | NH4Cl | 53.489 | 18.695 |
| Sodium chloride (this page) | NaCl | 58.43977 | 17.112 |
| Sodium nitrite | NaNO2 | 68.99477 | 14.494 |
| Sodium hypochlorite | NaClO | 74.43877 | 13.434 |
| Potassium chloride | KCl | 74.5483 | 13.414 |
| Ammonium nitrate | NH4NO3 | 80.043 | 12.493 |
| Sodium bicarbonate | NaHCO3 | 84.00577 | 11.904 |
Ordered by molar mass. The last column is 1000/M, which is the number a weighed gram actually gives you.