Planck length
The Planck length is about 1.616 × 10⁻³⁵ metres, the length you get by combining the gravitational constant, the speed of light and the reduced Planck constant into a quantity with the dimensions of length. It is roughly 10²⁰ times smaller than a proton, and nothing has ever been measured anywhere near it.
Watch out: Its numerical value inherits the uncertainty in G, which is the least precisely known of the fundamental constants, so the digits past the fourth are not solid.
| 1 | 1.6162550e-35 |
Where the unit came from
Max Planck derived the natural units in 1899 on the argument that a system built only from universal constants carries no arbitrary human choice in it. He had no quantum theory of gravity in mind; the length acquired that significance decades later.
One planck length in every length unit
| 1 | Planck length (lP)this unit | |
| 1.61625e-20 | femtometer (fm) | |
| 1.61626e-23 | picometer (pm) | |
| 3.05428e-25 | bohr radius (a0) | |
| 1.61626e-25 | angstrom (Å) | |
| 1.61625e-26 | nanometer (nm) | |
| 1.61626e-29 | micrometer (μm) | |
| 6.36321e-31 | thou (thou) | |
| 4.58151e-32 | point (pt) | |
| 1.61625e-32 | millimeter (mm) | |
| 3.81793e-33 | pica (pc) | |
| 1.61626e-33 | centimeter (cm) | |
| 6.36321e-34 | inch (in) | |
| 1.61625e-34 | decimeter (dm) | |
| 1.59080e-34 | hand (hh) | |
| 8.03435e-35 | link (li) | |
| 5.30267e-35 | foot (ft) | |
| 5.30266e-35 | US survey foot (ftUS) | |
| 1.76756e-35 | yard (yd) | |
| 1.61626e-35 | meter (m) | |
| 8.83779e-36 | fathom (ftm) | |
| 3.21374e-36 | rod (rd) | |
| 8.03435e-37 | chain (ch) | |
| 8.72708e-38 | cable length (cb) | |
| 8.03435e-38 | furlong (fur) | |
| 1.61626e-38 | kilometer (km) | |
| 1.00429e-38 | mile (mi) | |
| 8.72708e-39 | nautical mile (nmi) | |
| 3.34765e-39 | league (lea) | |
| 1.61626e-41 | megameter (Mm) | |
| 2.53689e-42 | Earth radius (REarth) | |
| 5.39125e-44 | light-second (ls) | |
| 4.20463e-44 | lunar distance (LD) | |
| 2.32321e-44 | solar radius (Rsun) | |
| 8.98541e-46 | light-minute (lmin) | |
| 1.08040e-46 | astronomical unit (AU) | |
| 1.70838e-51 | light-year (ly) | |
| 5.23793e-52 | parsec (pc) | |
| 5.23793e-55 | kiloparsec (kpc) | |
| 5.23793e-58 | megaparsec (Mpc) | |
| 5.23793e-61 | gigaparsec (Gpc) |
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