1 femtometre
1 fmLength · definition
The quantity is exact as entered. Comparisons use the clearly stated specimen, model or nominal measurement.
Length & distance
Just how long is 1 femtometre?
Microscopic
1 fm
1 femtometre
The quantity is exact as entered.
1 fmLength
0 - shared origin
Proton
A proton is a positively charged particle found in the nucleus of atoms, made up of quarks.
1.682 fmDiameter
0 - shared origin
Both rulers start at the same zero and share one linear scale. Artwork keeps its original proportions. A ruler represents the selected distance or a measurement not visible in this view.
A little perspective
The diameter of a proton is about 1.68 times 1 femtometre.
Measurements, assumptions & sources +
1 femtometre
Length: 1 fm; definition.
The quantity is exact as entered. Comparisons use the clearly stated specimen, model or nominal measurement.
Proton
Diameter: 1.682 fm; measured constant.
Twice the approximately 0.8409 fm charge radius. The charge distribution has no hard boundary; the illustration is schematic.
NIST — 2022 CODATA fundamental constants
The marked diameter is calibrated. Unmeasured illustration details are representative.
Measurement details
Why these numbers?
Compare 1 femtometre with the diameter of a proton. The notes below explain how each value was chosen.
Proton
1.682 fmDiameter · measured constant
Twice the approximately 0.8409 fm charge radius. The charge distribution has no hard boundary; the illustration is schematic.
- Comparing
- Length ↔ Diameter
- Relative size
- The diameter of a proton is about 1.68 times 1 femtometre. The diameter of a proton is approximately 68.2% greater than 1 femtometre.
How to read the visual
The diagram uses the recorded measurements. Details outside the marked spans do not set the scale.
- The diameter of a proton: This is a measured value; check the notes for its source and scope.
This comparison follows the selected length only; other dimensions may differ.
1 × 10⁻¹⁵ mmetres
3.2808 × 10⁻¹⁵ ftfeet
6.2137 × 10⁻¹⁹ mimiles
6.6846 × 10⁻²⁷ AUastronomical units
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