A nanometre (nm) is one billionth of a metre: 1 nm = 0.000000001 m, or 10⁻⁹ m. Put another way, there are a million nanometres in a millimetre and a thousand in a micrometre. The unit belongs to the SI system, in which nano is the prefix for a factor of 10⁻⁹.
What that means in practice
To get a feel for the scale:
- A human hair is roughly 50,000 to 100,000 nm thick
- Visible light has a wavelength of about 380 to 780 nm — which is why light colour is quoted in nanometres
- An ordinary paint film is several tens of micrometres thick, so tens of thousands of nanometres
- Coatings that change how a surface behaves without changing how it looks are often only a few to a few hundred nanometres thick
Where it appears in construction
- Glass — coatings on insulating glass units are ultra-thin. A metal oxide layer a few nanometres thick gives low-emissivity glass its performance, or reflects part of the solar radiation in solar control glass
- Surface treatment — water-repellent and dirt-shedding impregnations for facades, natural stone and sanitaryware work at the nanoscale, changing the contact angle of water droplets
- Insulation — aerogel owes its very low thermal conductivity to a pore structure in the order of tens of nanometres, which prevents air molecules from transferring heat efficiently
- Roughness and metrology — the surface roughness of metals and polished stone is quoted in nanometres or micrometres
- Light and colour — LED lighting and daylight are described by wavelength in nanometres; UV radiation lies below 380 nm and causes plastics and paint to degrade
Points to watch
- Do not confuse nanometre (nm) with micrometre (µm) or millimetre (mm) — for coating thicknesses the difference is a factor of a thousand
- The term “nano coating” is not a standardised claim. Ask for a technical data sheet with a measurable property, such as water absorption or service life, rather than relying on the prefix
- Ultra-thin layers are vulnerable to abrasion and harsh cleaners; always follow the manufacturer’s maintenance instructions
Related terms
- Micrometre
- Coating
- Aerogel
- Low-emissivity glass
- Impregnation
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.