| Nanometers (nm) | Chains (ch) |
|---|---|
| 1 Nanometer | 4.9709695379 × 10-11 ch |
| 2 Nanometers | 9.9419390758 × 10-11 ch |
| 3 Nanometers | 1.49129086137 × 10-10 ch |
| 4 Nanometers | 1.98838781516 × 10-10 ch |
| 5 Nanometers | 2.48548476895 × 10-10 ch |
| 10 Nanometers | 4.9709695379 × 10-10 ch |
| 20 Nanometers | 9.9419390758 × 10-10 ch |
| 25 Nanometers | 0.00000000124274238447 ch |
| 50 Nanometers | 0.00000000248548476895 ch |
| 100 Nanometers | 0.0000000049709695379 ch |
| Reference | Nanometers (nm) | Chains (ch) |
|---|---|---|
| A sheet of A4 paper (long side) | 297000000 nm | 0.0147638 ch |
| Average adult human height | 1.7 × 109 nm | 0.0845065 ch |
| A football pitch (length) | 1.05 × 1011 nm | 5.21952 ch |
| A marathon | 4.2195 × 1013 nm | 2097.5 ch |
| Height of Mount Everest | 8.849 × 1012 nm | 439.881 ch |
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.
The chain is a unit of length equal to 66 feet, 22 yards, or exactly 20.1168 metres. It occupies an unusual position in the imperial system as the unit that connected everyday measurement to land surveying.
It is named after a physical object. Edmund Gunter, an English mathematician, introduced a surveying chain of 100 iron links in 1620. The design solved a real problem: land area was recorded in acres, a unit inherited from medieval agriculture, while distances were measured in feet and yards. Gunter chose a length that reconciled the two systems. Ten square chains make exactly one acre, and 80 chains make one mile, so a surveyor could measure in chains and compute both area in acres and distance in miles without awkward conversion factors.
The chain shaped the landscape of several countries. The United States Public Land Survey System, which divided much of the American west into townships and sections from 1785, was laid out in chains. A section is one square mile, or 80 chains on a side, and the resulting grid remains visible in road patterns and field boundaries across the Midwest. Similar surveys in Canada, Australia and New Zealand used the same unit, and older property deeds in those countries still cite chain measurements.
Cricket preserves it in sporting form. The pitch measures 22 yards between the wickets, which is exactly one chain, a length fixed long before the game's laws were formally written.
British railways continue to use the chain for locating features along a line. Positions are recorded as a mileage and a chain figure, so 12 miles 40 chains identifies a point precisely. The convention survives in signalling diagrams and engineering records despite general metrication.
The chain subdivides into 100 links of 7.92 inches each, giving surveyors a decimal subdivision within an otherwise non-decimal system.
One chain equals 22 yards, 66 feet, or 20.1168 metres.