Skip to main content

Kilograms to Atomic Mass Units Converter

↔ Convert amu to kg instead

Common Conversions

kg amu
1e-27 0.6022
1e-26 6.022
1e-25 60.22
1e-24 602.2
1e-23 6022
1e-22 60221
1e-21 602214
1e-20 6022140
0.001 6.022e+23
0.01 6.022e+24
0.1 6.022e+25
1 6.022e+26

Why this conversion matters in chemistry

An atomic mass unit is defined as exactly one-twelfth the mass of a neutral C-12 atom, which works out to 1.66054 × 10⁻²⁷ kg. The conversion factor from kg to u is 6.02214 × 10²⁶ — exactly one thousand times Avogadro's number, which falls out cleanly because a gram of any substance contains Avogadro's number of u-equivalent units. Most chemistry never needs the kilogram side of this; we live on the u-scale through molar masses. The conversion shows up most often when a precision measurement reports an ion mass in kg through a Penning-trap cyclotron-frequency analysis and that result has to land in the u-scale of every molar-mass table in the textbook.

Formula

amu = kg × 6.02214 × 10²⁶

Worked Examples

1.66054×10⁻²⁷ kg = 1 amu

The defining identity — one u equals one-twelfth of a C-12 atom, which equals 1.66054 × 10⁻²⁷ kg.

1 kg = 6.022×10²⁶ amu

One kilogram on the u-scale — useful only for showing how many orders of magnitude separate macroscopic and atomic mass.

1.99265×10⁻²⁶ kg = 12 amu

The mass of a single C-12 atom — the reference point that anchors the entire u-scale.

0.001 kg = 6.022×10²³ amu

One gram in u, which equals Avogadro's number — the numerical coincidence behind why molar mass in g/mol matches atomic mass in u.

Frequently Asked Questions

How do I convert kg to u?
Multiply by 6.02214 × 10²⁶, which is one thousand times Avogadro's number. So 1.66054 × 10⁻²⁷ kg becomes 1 u, the defining anchor of the conversion.
What's the significance of the conversion factor?
It's 1000 × Nₐ, which shows up because a gram of any substance contains Nₐ atomic-mass units' worth of mass. The factor is what links the macroscopic kilogram to the molecular u-scale through the mole.
When does a chemist actually convert kg to u?
When a precision mass-spectrometry measurement reports a single-ion mass in SI kilograms and the result has to be expressed in u for comparison against a molar-mass table or a tabulated atomic mass evaluation. For ordinary stoichiometry the conversion stays implicit in g/mol.