How do I convert amu to kg?
Type a value in either box, and the answer shows it in the other unit as you type.
- Kilograms (kg)
- 1.66054 × 10⁻²⁷
1 u = 1.66054 × 10⁻²⁷ kg.
Kilograms (kg): 1.66054 × 10⁻²⁷. 1 u = 1.66054 × 10⁻²⁷ kg.
How to calculate
Converts atomic mass units (u) to kilograms (kg) and back, with the CODATA 2022 atomic mass unit.
Example with the default inputs (Atomic mass units (u) 1): 1 u = 1.66054 × 10⁻²⁷ kg.
Formula: kg = u × 1.66053906892 × 10⁻²⁷
- 1 u (unified atomic mass unit, or dalton) = 1.66053906892 × 10⁻²⁷ kg, the CODATA 2022 recommended value (NIST); it is measured, with a standard uncertainty of 0.00000000052 × 10⁻²⁷ kg (3.1 parts in 10¹⁰). The page converts with this value as if exact.
- Exact on the typed decimals: the answer shows 6 significant digits as d.ddddd × 10ⁿ (trailing zeros dropped), rounded half up; 0 shows as 0. A value above 0 whose answer is below 10⁻³⁰⁰ gives no answer.
Worked examples
Each example is checked against the calculator on every build.
- Atomic mass units (u) 1 gives Kilograms (kg) 1.66054 × 10⁻²⁷.Source: NIST CODATA 2022 value of the atomic mass unit (https://physics.nist.gov/cgi-bin/cuu/Value?ukg)
- Atomic mass units (u) 12 gives Kilograms (kg) 1.99265 × 10⁻²⁶.Source: NIST CODATA 2022 value of the atomic mass unit (https://physics.nist.gov/cgi-bin/cuu/Value?ukg)
Other questions people ask
How many kg is 1 amu?
1.66053906892 × 10⁻²⁷ kg, the CODATA 2022 value of the unified atomic mass unit (u), also called the dalton (Da). The page shows it to 6 significant digits: 1.66054 × 10⁻²⁷ kg.
How do I convert amu to kg?
Multiply by 1.66053906892 × 10⁻²⁷: kg = u × 1.66053906892 × 10⁻²⁷. So 12 u, the mass of one carbon-12 atom, is 1.99265 × 10⁻²⁶ kg, and 1,000 u is 1.66054 × 10⁻²⁴ kg.
Is the conversion exact?
No. The atomic mass unit is measured: CODATA 2022 gives a standard uncertainty of 0.00000000052 × 10⁻²⁷ kg, 3.1 parts in 10¹⁰. That is far below the 6 significant digits the page shows. The page converts with the recommended value as if it were exact.
How do I convert kg back to amu?
Divide by 1.66053906892 × 10⁻²⁷, or type the kilograms into the second box. 1 kg is about 6.022141 × 10²⁶ u.
What values can I convert?
From 0 to 1,000,000,000,000 u (10¹²), which is 1.66054 × 10⁻¹⁵ kg; a larger value gives no answer. A value above 0 whose answer is below 10⁻³⁰⁰ kg (below about 6.022 × 10⁻²⁷⁴ u) gives no answer either: "The answer is below 10⁻³⁰⁰, too small to show. Enter a larger value."