Moles to grams for sodium chloride is a multiplication by 58.439769 g/mol. A mole weighs 58.43977 g, 100 mmol weighs 5.84398 g, 10 mmol weighs 0.584398 g and a millimole is 58.4398 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. 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.
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 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
n- The amount of sodium chloride you need, in moles
58.439769- The molar mass of sodium chloride 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 58.439769 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 sodium chloride in grams
5 mmol × 58.43977 g/mol = 0.292199 g, which is 292.199 mg. Doubling the amount doubles the mass to 0.584398 g, because the relationship is a plain proportion once the molar mass is fixed.
250 mmol of sodium chloride in grams
250 mmol × 58.43977 g/mol = 14.6099 g, which is 14,609.9 mg. Doubling the amount doubles the mass to 29.2199 g, because the relationship is a plain proportion once the molar mass is fixed.
2 mol of sodium chloride in grams
2 mol × 58.43977 g/mol = 116.88 g, which is 116,880 mg. Doubling the amount doubles the mass to 233.759 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 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 many grams is one mole of sodium chloride?
58.439769 g, by definition of the molar mass. Two moles is 116.8795 g and half a mole is 29.21988 g.
How many grams is 0.1 mol, and how many milligrams is 1 mmol?
0.1 mol of sodium chloride is 5.84398 g. One millimole is 58.4398 mg and one micromole is 58.4398 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 0.5844 mg of sodium chloride, weigh 5.844 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, NaCl, at 58.439769 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 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.
| Wanted | Weigh (g) | Weigh (mg) | With 2% over (g) |
|---|---|---|---|
| 1 µmol | 0.000058 | 0.0584398 | 0.000060 |
| 10 µmol | 0.000584398 | 0.584398 | 0.000596086 |
| 100 µmol | 0.00584398 | 5.84398 | 0.00596086 |
| 1 mmol | 0.0584398 | 58.4398 | 0.0596086 |
| 10 mmol | 0.584398 | 584.398 | 0.596086 |
| 50 mmol | 2.92199 | 2921.99 | 2.98043 |
| 100 mmol | 5.84398 | 5843.98 | 5.96086 |
| 250 mmol | 14.6099 | 14,609.9 | 14.9021 |
| 500 mmol | 29.2199 | 29,219.9 | 29.8043 |
| 750 mmol | 43.8298 | 43,829.8 | 44.7064 |
| 1 mol | 58.4398 | 58,439.8 | 59.6086 |
| 2 mol | 116.88 | 116,880 | 119.217 |
| 5 mol | 292.199 | 292,199 | 298.043 |
| 10 mol | 584.398 | 584,398 | 596.086 |
Weigh is the amount multiplied by 58.439769 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 |
|---|---|---|---|
| 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.