Metric System Prefixes

A few real examples using distances as an attempt to get some sense of these different scales:

Quettametre Qm (1030m)

1Qm is ∼1,100 times larger than the diameter of the observable universe (∼8.8×1026m) (∼93 billion light-years)

theoretical bounds of the unobservable, post-inflationary universe >1Qm

Ronnametre Rm (1027m)

diameter of the observable universe is estimated at ∼0.88Rm (∼93 billion light-years)

...half of which is the distance to the Cosmic Microwave Background (CMB) edge: ∼0.44Rm (46.5 billion light-years)

largest known galactic superstructure (Hercules-Corona Borealis Great Wall) spans ∼0.095Rm (∼10 billion light-years)

Yottametre Ym (1024m)

diameter of the galaxy supercluster containing the Milky Way (Laniakea Supercluster): ∼4.9Ym (520 million light-years)

distance to Virgo cluster (the core cluster of our local supercluster) ∼0.51Ym (54 million light-years)

Zettametre Zm (1021m)

distance to Andromeda galaxy (M31): ∼23.6Zm (2.5 million light-years)

distance to Large Magellanic Cloud (satellite galaxy of the Milky Way): ∼1.5Zm (160,000 light-years)

diameter of the Milky Way: ∼1 to 1.4Zm (100,000 to 150,000 light-years)

Exametre Em (1018m)

distance to Deneb (in the constellation Cygnus): ∼24.6Em (2,600 light-years)

distance to Vega: ∼0.24Em (25 light-years)

Orion nebula (M42) spans ∼0.23Em (24 light-years)

Petametre Pm (1015m)

1 light-year: ∼9.46Pm (9,460,730,472,580,800m exactly)

distance to Proxima Centauri (the closest star system to the Sun): ∼40.1Pm (4.24 light-years)

outer limit of the Oort Cloud (the theoretical outer boundary of icy solar system bodies) extends up to 15Pm (∼100,000AU)

Terametre Tm (1012m)

Neptune's average distance from the Sun: 4.5Tm (30.1AU)

Saturn orbits the Sun at an average distance of 1.43Tm (9.58AU)

diameter of Betelgeuse: ∼1.2Tm (∼760 solar diameters)

Gigametre Gm (109m)

average distance to Sun (1AU): ∼149.6Gm (149,597,870.7km)

diameter of the Sun: ∼1.39Gm (1,392,700km)

average distance to the Moon: 0.384Gm (384,400km)

Megametre Mm (106m)

length of the Great Wall of China (including all branches): ∼21.2Mm (21,196km)

diameter of the Moon: ∼3.47Mm (3,474km)

straight-line distance from London to Barcelona: ∼1.14Mm (1,140km)

Kilometre km (103m)

width (East to West) of the Isle of Wight: ∼36km

length of the QE2 bridge: 2.8km

height of The Shard: 0.31km (309.6m)

Hectometre hm (102m)

height of SLS Block 1 rocket (used in the Artemis I and II missions): 0.98hm (98m)

length of major-tournament football pitch: 1.05hm (105m)

100-metre sprint track: 1.0hm (100m) ...obviously!

Decametre dam (101m)

length of an adult blue whale: 2.5 - 3dam (25-30m)

length of a tennis court: ∼2.4dam (23.77m)

height of an average two-story house: ∼0.7dam (∼7m)

Metre m (100m)

height of a standard internal doorway: ∼2m (198.1cm = 6ft 6in)

length of an acoustic guitar: ∼1m

width of a single mattress: 0.9m

Decimetre dm (10-1m)

height of a classic 330ml drink can: ∼1.2dm (∼11.5cm)

width across an adult human palm: ∼1dm (10cm)

length of a £10 note: 1.32dm (13.2cm)

Centimetre cm (10-2m)

diameter of a £1 coin: 2.34cm

diameter of an AA battery: 1.45cm

width of an adult thumbnail: ∼1 - 1.5cm

Millimetre mm (10-3m)

length of a sesame seed: ∼2- 3mm

thickness of a 1p coin: 1.65mm

thickness of a credit card: ∼0.76mm

Micrometre µm (10-6m)

diameter of human hair: 50 - 100µm

diameter of human red blood cell: ∼6 - 8µm

length of E. coli bacterium: ∼1 - 2µm

Nanometre nm (10-9m)

visible light wavelength: red ∼650nm - violet ∼400nm

diameter of the SARS-CoV-2 (COVID) virus: ∼100nm

width of a DNA strand: ∼2.0nm

Picometre pm (10-12m)

length of a Carbon-Carbon single bond: ∼154pm (0.154nm)

empirical diameter of a Hydrogen atom: ∼106pm (Bohr radius ∼53pm)

wavelength of high-energy gamma-ray photons: <10pm

Femtometre fm (10-15m)

diameter of a lead-208 atomic nucleus: ∼11 - 12fm

effective operating distance of Strong Nuclear Force: ∼1 - 3fm

radius of a proton's charge distribution: ∼0.84fm

Attometre am (10-18m)

LIGO detector measures displacement variations in interferometer mirrors down to 1am (∼1/1,000th the width of a proton)

high-energy scattering experiments constrain the physical radius of an electron to less than 1am

Zeptometre zm (10-21m)

effective interaction range mediated by W and Z bosons (Weak Nuclear Force): ∼1 - 2zm

protons accelerated to 7TeV at the Large Hadron Collider have a quantum de Broglie wavelength of ∼0.2zm

Yoctometre ym (10-24m)

the top quark's reduced Compton wavelength (at a mass of ∼173GeV/c2): ∼1.1ym

quantum wavelengths of cosmic rays with energies near 1020eV (ultra-high-energy): ∼0.01 - 1ym

Rontometre rm (10-27m)

wavelength of exa-electronvolt (EeV) cosmic neutrinos: the order of 1rm

theoretical scale of force unification (Grand Unified Theory (GUT) ∼1016GeV) corresponds to a quantum length scale of ∼0.02rm

Quectometre qm (10-30m)

hypothesized length scale of vibrating 1D strings in quantum gravity string theory: 1 - 0.00001qm

1qm is ∼61,800 Planck lengths (the theoretical quantum resolution limit of spacetime - ℓₚ ∼1.616 × 10-35m)