About

The ångström (Å) and the nanometre (nm) both describe atomic-scale lengths, yet confusing them introduces a factor-of-ten error that corrupts lattice parameters, spectral calibrations, and thin-film specifications. One ångström equals exactly 0.1 nm, a definition rooted in the SI relationship 1 Å = 10⁻¹⁰ m. X-ray crystallography databases (ICSD, CSD) report bond lengths in Å, while semiconductor fabrication and optical spectroscopy increasingly use nm. This converter handles both directions with configurable significant figures, so transcription between datasheets and simulation inputs stays exact.

The tool approximates nothing. The conversion factor is a fixed decimal shift. Precision loss arises only from floating-point representation at extreme magnitudes (beyond 10¹⁵), which is flagged automatically. Pro tip: when pulling lattice constants from older literature, verify whether the author used the pre-1907 ångström definition, which differed by about 5 parts per million from the modern SI-aligned value.

Formulas

The conversion relies on the exact SI definition of the ångström:

1 Å ≡ 10⁻¹⁰ m = 0.1 nm

Therefore, to convert from ångströms to nanometres:

L_nm = L_Å × 0.1

And the inverse:

L_Å = L_nm × 10

Where L_nm is the length in nanometres and L_Å is the length in ångströms. The conversion factor 0.1 is exact with zero uncertainty, as both units are defined relative to the metre.

Reference Data

Quantity	Value (Å)	Value (nm)	Context
Bohr radius (a₀)	0.529	0.0529	Hydrogen atom ground state
C - C single bond	1.54	0.154	Diamond, alkanes
C=C double bond	1.34	0.134	Ethylene
O - H bond length	0.96	0.096	Water molecule
Si lattice constant	5.431	0.5431	Silicon crystal (300 K)
Cu Kα X-ray	1.5406	0.15406	Common diffractometer source
Mo Kα X-ray	0.7107	0.07107	Single-crystal diffraction
UV-C boundary	2800	280	Germicidal wavelength limit
Visible light (violet)	3800	380	Short-wavelength visible
Visible light (green)	5500	550	Peak human eye sensitivity
Visible light (red)	7000	700	Long-wavelength visible
Near-IR telecom	15500	1550	Fiber optic C-band
DNA helix diameter	20	2.0	B-form double helix
Graphene C - C spacing	1.42	0.142	sp² carbon
NaCl lattice constant	5.640	0.5640	Rock salt structure
GaAs lattice constant	5.653	0.5653	III-V semiconductor
Van der Waals radius (He)	1.40	0.140	Noble gas
Protein α-helix pitch	5.4	0.54	Per turn (3.6 residues)
EUV lithography	135	13.5	Next-gen chip fabrication
Hydrogen atom diameter	1.06	0.106	Approximate covalent

Frequently Asked Questions

Interatomic distances in crystals typically fall between 0.5 Å and 6 Å. Using nanometres would place most values below 1, requiring leading zeros that increase transcription errors. The ångström keeps bond lengths as convenient single-digit numbers. The International Union of Crystallography continues to accept Å as the conventional unit for structural data.

No. The SI unit of length is the metre. The ångström (1 Å = 10⁻¹⁰ m) is a non-SI unit accepted for use with SI by the BIPM due to its widespread adoption in spectroscopy and crystallography. The NIST and ISO 80000-1 list it as a recognized non-SI unit.

IEEE 754 double-precision floats carry about 15 - 17 significant decimal digits. Since the conversion is a simple multiplication by 0.1 (which is not exactly representable in binary), values beyond roughly 10¹⁵ Å may show rounding artifacts in the last digit. For practical atomic-scale work, this is never a concern. This tool flags when results may lose precision.

Anders Ångström originally defined his unit in 1868 based on the cadmium red line. In 1907 the International Astronomical Union redefined it relative to the metre, introducing a discrepancy of about 5 parts per million. The modern definition (1 Å = 10⁻¹⁰ m exactly) has been standard since mid-20th century. Pre-1907 literature may carry this systematic offset.

Yes. Visible light spans approximately 3800 Å to 7000 Å, or equivalently 380 nm to 700 nm. The presets include common spectral boundaries. Note that this converter handles length units only. It does not compute frequency or energy from wavelength.

Modern X-ray diffractometers report lattice constants to 4 - 5 significant figures (e.g., silicon at 5.4310 Å). Set the significant figures control in this tool to match your source data precision. Reporting more digits than your measurement supports implies false accuracy.