Water molecule
A water molecule is a group of two hydrogen atoms bonded to one oxygen atom. Its bent arrangement gives water many of its distinctive properties.
How big is it?
280 pm · characteristic size
Characteristic size · representative
A little perspective
Water molecule vs Hydrogen atom: length comparison
The characteristic size of a water molecule is about 2.65 times the characteristic size of a hydrogen atom.
A water molecule is a group of two hydrogen atoms bonded to one oxygen atom.
A hydrogen atom is the simplest neutral atom, with one proton in its nucleus and one electron around it.
Both rulers start at the same zero and share one linear scale. Artwork keeps its original proportions.
Measurements, assumptions & sources +
Water molecule
Characteristic size: 280 pm; representative.
A chosen 0.28 nm molecular-scale model. Effective molecular size depends on the definition.
University of Utah — Cell size and scale
The marked characteristic size is calibrated. Unmeasured illustration details are representative.
Hydrogen atom
Characteristic size: 105.8 pm; representative.
A diameter of twice the Bohr radius, used as a characteristic scale. An electron cloud has no hard outer surface.
NIST — 2022 CODATA fundamental constants
The marked characteristic size is calibrated. Unmeasured illustration details are representative.
Use the visual comparison to explore its scale, then check the measurements and sources.
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Why this measurement?
Why we use 280 pm
We compare the characteristic size of a water molecule. This is a representative comparison value; individual specimens or conditions can vary.
A chosen 0.28 nm molecular-scale model. Effective molecular size depends on the definition.
The marked horizontal span follows the measured feature, not the edges of the image. How calibrated comparisons work →
Recorded properties
Dimensions and measurements
| Property | Selected value | Recorded range | Basis |
|---|---|---|---|
| 280 pm | Not recorded | representative | |
| 2.992 × 10⁻²⁶ kg | Not recorded | representative |
Around this scale
Explore nearby values.
Compare examples with lower, similar and higher values. Each card names the measurement being compared.
Nearest lower valueMicroscopic objectsHydrogen atom105.8 pmCharacteristic sizeA hydrogen atom is the simplest neutral atom, with one proton in its nucleus and one electron around it.
Nearest higher valueMicroscopic objectsGlucose molecule1 nmCharacteristic sizeA glucose molecule is a simple sugar used by living cells as a source of chemical energy.Sources and method
Want to check the number?
The source records and measurement method remain available for inspection.
- University of Utah — Cell size and scaleApproximate biological size regimes. Atlas specimens and geometric assumptions are individually labelled.
More ways to see it
Curated comparisons
There’s always another scale
Follow your curiosity.
Fundamental physicsProton1.682 fmA proton is a positively charged particle found in the nucleus of atoms, made up of quarks.
MicroscopicCell10 µmA cell is the basic structural unit of living organisms.
PeopleHair70 µmA hair is a slender strand of protein that grows from the skin of humans and other mammals.MicroscopicHydrogen atom105.8 pmA hydrogen atom is the simplest neutral atom, with one proton in its nucleus and one electron around it.MicroscopicGlucose molecule1 nmA glucose molecule is a simple sugar used by living cells as a source of chemical energy.Fundamental physicsBohr radius52.92 pmThe Bohr radius is a fundamental physical constant representing the most probable distance between the nucleus and the electron in a hydrogen atom according to early quantum theory.
MicroscopicDNA double helix2 nmDNA is the molecule that stores hereditary information in living organisms.
MicroscopicIgG antibody molecule14.5 nmAn IgG antibody molecule is a Y-shaped protein produced by the immune system to identify and neutralise foreign substances.