# Atomic Mass Unit: Converting to kgs

• kat_r
In summary, you can convert the atomic mass unit into kilograms by multiplying by 1.661 and rounding to the nearest thousandth.
kat_r
how do you convert the atomic mass unit into kgs?

kat_r said:
how do you convert the atomic mass unit into kgs?

Atomic Mass Unit - Kilogram
(Ref: NIST)

{1 amu ≅ 1.66053886 x 10(-27) kg}
{Standard Uncertainty: 0.00000028 x 10(-27) kg}
{Relative Standard Uncertainty: 1.7 x 10(-7)}

(Corrected Thanks To Curious3141, et. al.)
~~

Last edited:
I'm afraid that isn't correct, xanthym.

1 atomic mass unit = 1.660538 × 10^(-27) kilograms

It should be the same order of magnitude as a proton's mass. What you quoted is electron mass.

Curious 3141 is right; that first post is wrong. He gave the mass of an electron. Curious 3141's value should be right (I remember it being 1.66 x 10^-27 kg = 1 amu)

If you wanted to derive it, you could remember that 1 amu is defined as 1/12 the mass of a carbon 12 atom, which, by definition of the mole, I believe, has a molar mass of 12 g/mol. So if you have 6.022 x 10^23 atoms (1 mole of atoms) of Carbon-12, you'll have (6.022 x 10^23 atoms)(12 amu/atom) = (12 g)(1 kg/1000 g)

Which comes out to: 7.2264 x 10^24 amu = 0.012 kg

Divide both sides by 7.2264 x 10^24, and you get:

1 amu = 1.661 x 10^-27 kg <--- with significant figures.

I'm pretty sure the reasoning behind that method of derivation is sound. In any case, it gets you the right result. The only reason I wonder about it is because, I know that carbon-12 is defined as having exactly 12 amu, and I'm pretty sure that one mole of atoms is defined as the number of atoms required to achieve a mass, in grams, whose numerical value is equal to the numerical value of amu (so a mole of carobon-12, which is 12 amu exactly, will have a mass of 12 grams exactly).

Anyway. Yeah. Curious is right.

Last edited:
It's interesting that he edited the message 9 minutes later...

When u give physical constants with nonexact values,don't use the "=" sign,unless you give the uncertainty in that value...Use the approximately equal sign.

[tex] 1\mbox{amu}\simeq 1.66\cdot 10^{-27}\mbox{Kg} [/itex]

Daniel.

kat_r said:
how do you convert the atomic mass unit into kgs?
(Original Msg Corrected Thanks To Curious3141, et. al.):

Atomic Mass Unit - Kilogram
(Ref: NIST)

{1 amu ≅ 1.66053886 x 10(-27) kg}
{Standard Uncertainty: 0.00000028 x 10(-27) kg}
{Relative Standard Uncertainty: 1.7 x 10(-7)}

~~

I said it had significant figures, thus implying it was not exact.

I don't exactly have one of those squiggly approximately equal-to signs on my keyboard, and I don't know how to make the images you seem to be able to use on the forum here, since I'm new.

And if you're typing, you should spell out your words like "you" instead of writing "u," but I knew what you meant. Nonetheless, your comment has been noted.

Last edited:
Night Owl said:
Curious 3141 is right; that first post is wrong. He gave the mass of an electron. Curious 3141's value should be right (I remember it being 1.66 x 10^-27 kg = 1 amu)

If you wanted to derive it, you could remember that 1 amu is defined as 1/12 the mass of a carbon 12 atom, which, by definition of the mole, I believe, has a molar mass of 12 g/mol. So if you have 6.022 x 10^23 atoms (1 mole of atoms) of Carbon-12, you'll have (6.022 x 10^23 atoms)(12 amu/atom) = (12 g)(1 kg/1000 g)

Which comes out to: 7.2264 x 10^24 amu = 0.012 kg

Divide both sides by 7.2264 x 10^24, and you get:

1 amu = 1.661 x 10^-27 kg <--- with significant figures.

I'm pretty sure the reasoning behind that method of derivation is sound. In any case, it gets you the right result. The only reason I wonder about it is because, I know that carbon-12 is defined as having exactly 12 amu, and I'm pretty sure that one mole of atoms is defined as the number of atoms required to achieve a mass, in grams, whose numerical value is equal to the numerical value of amu (so a mole of carobon-12, which is 12 amu exactly, will have a mass of 12 grams exactly).

Anyway. Yeah. Curious is right.

Seems familiar to u,alias you...? Oh,"~" is a good sign to use,unless u know how to edit in LaTex...

Daniel.

## 1. What is an atomic mass unit (amu)?

An atomic mass unit (amu) is a unit of measurement used to express the mass of an atom or molecule. It is defined as one-twelfth of the mass of a carbon-12 atom.

## 2. How is atomic mass unit (amu) related to kilograms (kg)?

1 amu is equal to 1.66054 x 10^-27 kg. This means that the mass of an atom in amu is equivalent to its mass in kg multiplied by this conversion factor.

## 3. Why is it necessary to convert atomic mass units to kilograms?

Converting from amu to kg allows for more precise and accurate measurements of atomic and molecular masses. This is especially important in scientific research and calculations.

## 4. How do you convert from atomic mass units to kilograms?

To convert from amu to kg, simply multiply the number of amu by 1.66054 x 10^-27 kg. For example, if an atom has a mass of 20 amu, its mass in kg would be 20 x 1.66054 x 10^-27 = 3.32108 x 10^-26 kg.

## 5. Can atomic mass units and kilograms be used interchangeably?

No, atomic mass units and kilograms are not interchangeable units. They are used to measure different quantities (mass at the atomic level vs. mass at the macroscopic level) and therefore require conversion between the two units.

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