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Grams to Atomic Mass Units Converter
↔ Convert amu to g instead

Common Conversions

g amu
1e-27 0.000602
1e-26 0.00602
1e-25 0.0602
1.661e-24 1
1e-23 6.022
1.993e-23 12
2.656e-23 15.999
1e-22 60.22
1e-20 6022
1e-10 60220000000000
1 6.022e+23

Why this conversion matters in chemistry

Grams and amu describe mass at two radically different scales — benchtop and atomic — but they're tied together by a clean definitional relationship. Avogadro's number of amu is exactly 1 gram. So 1.000 g of carbon-12 is 6.022 × 10²³ u in total mass, which works out to exactly 5.018 × 10²² atoms each weighing 12.000 u. The conversion is multiplying by Avogadro's number (6.022 × 10²³), which is the same as dividing by the amu-to-grams factor (1.66054 × 10⁻²⁴ g/u). The real use case is computational: bulk-experimental measurements come in grams, quantum-mechanical calculations live in per-particle u, and the conversion is what lets the two meet.

Formula

amu = g × 6.02214 × 10²³

Worked Examples

1.661 × 10⁻²⁴ g = 1 amu

The defining mass of one atomic mass unit — 1/12 of a carbon-12 atom, pinned by convention.

1 g = 6.022 × 10²³ amu

Avogadro's number of amu. The elegant equivalence that lets macroscopic mass and atomic mass share numerical values.

2.656 × 10⁻²³ g = 15.999 amu

The mass of a single oxygen atom. Small, exact, and the anchor for most elemental mass calculations.

3.351 × 10⁻²³ g = 20.180 amu

The mass of a single neon atom, using the standard atomic weight of 20.180 u.

Frequently Asked Questions

How do I convert grams to amu?
Multiply by Avogadro's number (6.022 × 10²³). So 1 g becomes 6.022 × 10²³ amu. The factor works because 1 amu is defined as 1.66054 × 10⁻²⁴ g — essentially 1/Nₐ in gram units.
How are amu and molar mass related?
The molar mass in g/mol is numerically identical to the atomic or molecular mass in amu. Carbon has an atomic mass of 12.011 amu and a molar mass of 12.011 g/mol — same number, different units. This equivalence is deliberate, baked into how the amu and the mole were defined.
What exactly is an atomic mass unit?
One amu — also called the unified atomic mass unit (u) or dalton (Da) — is defined as exactly 1/12 the mass of a carbon-12 atom, or 1.66054 × 10⁻²⁴ g. It exists to keep atomic-scale masses in readable numbers: hydrogen is about 1 amu, oxygen about 16, a typical organic molecule in the hundreds.
Are amu, u, and dalton interchangeable?
Yes, all three describe the same quantity: 1/12 the mass of ¹²C. IUPAC officially prefers u or Da. Biochemistry leans toward daltons (often kDa for proteins). Most introductory chemistry texts still use amu. The numerical value is identical regardless of notation.