| Hectometers (hm) | Nanometers (nm) |
|---|---|
| 1 Hectometer | 100000000000 nm |
| 2 Hectometers | 200000000000 nm |
| 3 Hectometers | 300000000000 nm |
| 4 Hectometers | 400000000000 nm |
| 5 Hectometers | 500000000000 nm |
| 10 Hectometers | 1000000000000 nm |
| 20 Hectometers | 2000000000000 nm |
| 25 Hectometers | 2500000000000 nm |
| 50 Hectometers | 5000000000000 nm |
| 100 Hectometers | 10000000000000 nm |
| Reference | Hectometers (hm) | Nanometers (nm) |
|---|---|---|
| A sheet of A4 paper (long side) | 0.00297 hm | 297000000 nm |
| Average adult human height | 0.017 hm | 1.7 × 109 nm |
| A football pitch (length) | 1.05 hm | 1.05 × 1011 nm |
| A marathon | 421.95 hm | 4.2195 × 1013 nm |
| Height of Mount Everest | 88.49 hm | 8.849 × 1012 nm |
The hectometre is one hundred metres, written hm. It uses the SI prefix hecto, from the Greek hekaton meaning hundred. Like the decametre and the decimetre it is a legitimate unit that ordinary usage has largely bypassed in favour of metres and kilometres.
Its clearest application is in land measurement, where it appears indirectly. A square hectometre is 10,000 square metres, which is exactly one hectare. The hectare is the standard unit of land area in agriculture, forestry and property registration across most of the world, so the hectometre is embedded in daily practice even though the length itself is seldom named. A square field measuring one hectometre on each side covers one hectare.
Rail and road infrastructure provides the other common use. Several European railway networks mark distances with hectometre posts, placing a marker every hundred metres along the track. These give maintenance crews and signallers a precise location reference, and incident reports commonly cite a kilometre and hectometre figure. Dutch and Belgian motorways use hectometre markers in the same way, and drivers are directed to quote them when reporting a breakdown.
Athletics offers a familiar length without using the name. The straight of a standard outdoor track is one hectometre, and the 100 metres is the shortest standard sprint distance. Nobody calls it the one-hectometre sprint.
Meteorology uses the unit for cloud base height in some aviation reporting formats, where reporting in hundreds of metres or hundreds of feet keeps the figures compact.
Nautical charts and aviation both work in comparable steps without adopting the name. Runway visual range is reported in hundreds of metres in many countries, and visibility in aviation weather reports is given in metres up to five thousand, effectively in hectometre increments. Where the unit is used explicitly, as on Dutch motorways, its advantage is precision: a hectometre marker locates an incident to within fifty metres.
Radio engineering names a whole band after it. The international classification calls waves between 100 and 1000 metres hectometric, corresponding to frequencies from 300 kilohertz to 3 megahertz, and that band is the medium wave used for broadcasting since the 1920s. A transmitter working at 1000 kilohertz radiates a wave three hectometres long, which is why medium-wave aerials are tall masts rather than the short whips that serve higher frequencies. The naming continues in both directions: the band below is kilometric and the one above decametric, so the ladder of metric prefixes maps directly onto the divisions of the radio spectrum.
One hectometre equals 100 metres, 10 decametres, or 0.1 kilometres. It is approximately 328.084 feet, or 109.361 yards.
The nanometre is one billionth of a metre. It is formed by applying the SI prefix nano, meaning 10-9, to the metre, and is written nm. The prefix derives from the Greek nanos, meaning dwarf.
This is the working scale of modern optics and electronics. Visible light spans roughly 380 nm at the violet end to 750 nm at the red end, which makes the nanometre the standard unit for describing colour in physical terms. A laser pointer emitting at 532 nm is green; one at 650 nm is red. Ultraviolet light falls below 380 nm and infrared above 750 nm.
Biology uses the unit constantly. The DNA double helix is about 2 nm across. A typical virus measures between 20 and 300 nm. Cell membranes are around 7 nm thick. These dimensions sit below the resolution of conventional light microscopes, which is limited by the wavelength of the light itself to roughly 200 nm.
Semiconductor manufacturing made the nanometre familiar outside science. Process nodes have been labelled 90 nm, 45 nm, 14 nm, 5 nm and smaller. The figure no longer corresponds to any single measurable feature on the chip, having become a marketing designation rather than a physical dimension, but the underlying structures genuinely are nanometres across. A modern transistor gate is a few tens of atoms wide.
Nanotechnology takes its name from the unit and conventionally covers structures between 1 and 100 nm. Materials often behave differently in this range because surface effects begin to dominate bulk properties.
Measuring at this scale requires instruments that do not rely on visible light. Electron microscopes resolve features below one nanometre by using electrons, whose effective wavelength is far shorter than that of light. Atomic force microscopes work differently again, dragging a sharp tip across a surface and recording its deflection. Both were essential to the development of nanotechnology, since a field cannot advance far while its subject matter remains invisible.
One nanometre equals 10 ångströms, 1000 picometres, or 0.001 micrometres. A sheet of paper is roughly 100,000 nm thick.