Micrometer, Nanometer & Ångström Converter

Understanding the micrometer and nanometer converter — concept and principle

Very small lengths appear everywhere in science and manufacturing: light wavelengths in nanometres, atomic spacings in ångströms or picometres, particle and fibre sizes and coating thicknesses in micrometres, and film or sheet thickness in mils (thousandths of an inch) in US documents. This converter switches between micrometres (µm), nanometres (nm), ångströms (Å), picometres (pm), millimetres (mm), mils and metres.

Each metric prefix step is ×1,000; the ångström sits between nm and pm at 0.1 nm.

How it is calculated

Values are converted to micrometres and then to the target unit: result = value × (µm per "from" unit) ÷ (µm per "to" unit). All factors are exact:

1 µm = 10⁻⁶ m = 0.001 mm
1 nm = 0.001 µm = 10⁻⁹ m
1 Å = 0.1 nm = 0.0001 µm = 10⁻¹⁰ m
1 pm = 0.001 nm = 10⁻¹² m
1 mil (thou) = 0.001 in = 25.4 µm

The principle

The metric prefixes step by factors of 1,000: milli (10⁻³), micro (10⁻⁶), nano (10⁻⁹), pico (10⁻¹²). Moving one prefix smaller multiplies the number by 1,000, which is why 1 µm = 1,000 nm and 1 nm = 1,000 pm. The ångström is not an SI unit but is still widely used in crystallography and chemistry because typical atomic radii and bond lengths are around 1 Å (bond lengths are often 1–2 Å). The mil comes from the inch: since 1959 the inch is exactly 25.4 mm, so one thousandth of an inch is exactly 25.4 µm.

Worked example

Inputs: value = 1, from micrometres, to nanometres.
1 µm × 1 ÷ 0.001 = 1,000 nm.
Other units: 10,000 Å; 1,000,000 pm; 0.001 mm; 0.000001 m.
In mils: 1 ÷ 25.4 = 0.0393700787 mil.

How to read the result

Familiar scales make the numbers meaningful. Visible light spans roughly 380–780 nm. A human hair is commonly several tens of micrometres thick, though it varies widely. Fine dust labelled PM2.5 means particles with a diameter of 2.5 µm or less, and PM10 means 10 µm or less. Coating and paint thickness are often specified in µm (or mils in US sources), and 1 mil is about 25 µm.

Common mistakes

Confusing "mil" (a thousandth of an inch) with "mm" or with the angular mil used in artillery.
Writing "micron" and "µm" as different units; micron is an older name for the micrometre.
Typing "m" in place of µ in documents, which turns micro into milli, a factor of 1,000.

Keep in mind: Converting a unit does not change measurement uncertainty. At the nanometre scale, the result depends heavily on the instrument and method, so report measured values with their stated precision.

Frequently asked questions

How many nanometres are in a micrometre?

Exactly 1,000 nm.

How big is an ångström?

10⁻¹⁰ m, or 0.1 nm, which is on the order of the size of an atom.

How many micrometres is 1 mil?

Exactly 25.4 µm, so 2 mil is 50.8 µm.

Sources: BIPM, The International System of Units (SI Brochure), 9th edition, 2019 · NIST Special Publication 811 (2008), Appendix B

Checked 8 Nov 2026. Factors from the SI Brochure (BIPM, 9th ed.) and NIST Special Publication 811 (2008), Appendix B.