Daltons to Grams per Mole Converter
Common Conversions
| Da | g/mol |
|---|---|
| 1 | 1 |
| 10 | 10 |
| 18.015 | 18.015 |
| 58.44 | 58.44 |
| 100 | 100 |
| 180.16 | 180.16 |
| 342.3 | 342.3 |
| 1000 | 1000 |
| 10000 | 10000 |
| 66500 | 66500 |
| 100000 | 100000 |
| 1000000 | 1000000 |
Why this conversion matters in chemistry
The dalton describes the mass of a single molecule, written in atomic mass units. Grams per mole describes a mole of those molecules. The two units are numerically the same — a peptide with a measured mass of 5807.6 Da has a molar mass of 5807.6 g/mol — because the gram is defined as Avogadro's number of u. The conversion is the identity, but it sits at a useful junction in any workflow that moves between mass spectrometry and stoichiometry. An MS-determined insulin mass of 5808 Da becomes the 5808 g/mol that a dosing-mass calculation needs without any further arithmetic.
Formula
Where the factor comes from
Da and u name the same unit. The dalton is the form mass spectrometry and biochemistry settled on, and it was accepted for use alongside the SI under that name. The algebra is therefore the ordinary route from a per-particle quantity to a per-mole one: take the molecular mass in kilograms per particle, multiply by Nₐ particles per mole, then express the result in grams. Those two large factors very nearly cancel, because Nₐ × mᵤ is the molar mass constant and that constant sits within about one part in 10⁹ of 1 g/mol. What survives is a factor of one. Note what the conversion does not settle: whether the dalton figure is a monoisotopic or an average mass. That choice is made upstream, and no arithmetic here repairs it.
Precision and significant figures
The identity preserves every digit, so precision is decided entirely by which mass the spectrometer reported. Monoisotopic and average masses differ by roughly five parts in ten thousand for ordinary organic composition — glucose is 180.063 against 180.156, a gap of 0.09 — and the difference grows in absolute terms with size, reaching tens of daltons across a protein of a few tens of kilodaltons. Stoichiometry wants the average, since a weighed sample contains the natural isotope mix. Quoting a peptide molar mass to four decimals from a monoisotopic measurement is precise about a quantity the gravimetric calculation was never asking for.
Worked Examples
Water — the most-cited reference for the identity, since the same value lives in every general-chemistry textbook.
Sucrose — the disaccharide whose molar mass anchors a lot of carbohydrate-chemistry calculations.
Bovine serum albumin — the protein-chemistry molar-mass workhorse, equivalent to 66.5 kDa.
Sodium chloride — the textbook molar-mass example, with the same number in both unit conventions.
Common mistakes
Monoisotopic mass used as molar mass
A monoisotopic peak reports the all-light-isotope species, every carbon a ¹²C. Material on a balance contains the natural mix, so its molar mass is the abundance-weighted average, always the larger number. The gap is negligible for a tripeptide and tens of daltons for a protein, and it rides straight into any concentration calculated from a weighed mass.
m/z is not mass
Electrospray spectra plot mass-to-charge ratio, and a multiply-charged ion sits at a fraction of its neutral mass. A peak at 1000 m/z on a 10+ ion belongs to a species near 9990 Da once the ten added protons are accounted for. Reading the axis value straight into g/mol understates the molar mass by an order of magnitude.
The measured species is not the reagent
Mass spectrometry sees whichever ion flew: a sodium adduct, a free base where the bottle holds a hydrochloride, an anhydrous form where the solid is a dihydrate. The molar mass a weighing needs is that of the material actually on the balance, counterion and waters of hydration included. Settle the form before the dalton figure becomes a g/mol figure.