Angstroms to Picometers Converter
Common Conversions
| Å | pm |
|---|---|
| 0.5 | 50 |
| 0.96 | 96 |
| 1 | 100 |
| 1.21 | 121 |
| 1.34 | 134 |
| 1.54 | 154 |
| 2 | 200 |
| 3 | 300 |
| 3.4 | 340 |
| 5 | 500 |
| 10 | 1000 |
Why this conversion matters in chemistry
Crystallography still runs on ångströms — the CIF files for small-molecule structures tabulate bond lengths in Å because the numbers are convenient (C–C at 1.54 Å, C=O at 1.23 Å, aromatic C–C at 1.40 Å). IUPAC has been pushing for picometers as the strict SI replacement, which keeps the same precision but uses whole-number values (154 pm, 123 pm, 140 pm). Multiplying by 100 does the conversion. Both units are accepted across the chemistry literature, and there's no real pressure for a universal switch. Being fluent both directions is what lets you read across older and newer structural papers without stumbling.
Formula
Where the factor comes from
Pico is 10⁻¹², two decades below the angstrom's 10⁻¹⁰, which makes this the one conversion in the angstrom family that moves the decimal point without producing a leading zero or forcing scientific notation. A bond length in the usual 0.9 to 3 Å range becomes a two- or three-digit number: 1.54 turns into 154, 0.96 into 96. Both sides are exact — the picometer is the meter rescaled by a defined prefix, the angstrom is fixed at 10⁻¹⁰ m by convention — so the factor of 100 is a stipulation with no measurement anywhere inside it. That readability is the whole argument behind IUPAC's preference for picometers here: strict SI without the awkward decimals nanometers would impose at atomic scale.
Precision and significant figures
The picometer's real advantage is that it is about the size of a crystallographic uncertainty. Standard uncertainties on refined bond lengths run roughly 0.002 to 0.005 Å, which is 0.2 to 0.5 pm, so a value written as 154.0(3) pm puts the doubt in the last figure where it can be read at a glance. That bracketed su rides through the conversion untouched, since value and uncertainty scale by the same 100. The hazard runs the other way: a two-figure 1.5 Å becomes 150 pm, and those trailing zeros now look like digits somebody measured. Write 1.5 × 10² pm, or stay in angstroms.
Worked Examples
The defining equivalence. An ångström is exactly a hundred picometers.
A C–C single bond. The reference value most organic chemistry is calibrated against.
The O–H bond length in water. Short even by molecular standards — oxygen pulls its hydrogen in tight.
The spacing between stacked base pairs in B-form DNA. An iconic number in structural biology.
Common mistakes
Trailing zeros claim figures nobody measured
Multiplying by 100 appends two zeros, and a reader has no way to distinguish a measured zero from a placeholder. A distance given as 2.4 Å carries two significant figures; rendered as 240 pm it reads as three. Where the figure count matters — comparing against an optimized geometry, say — write 2.4 × 10² pm and the ambiguity disappears.
Radii tables use incompatible definitions
Covalent, ionic, van der Waals and metallic radii are all published in picometers and none of them are interchangeable. An ionic radius depends further on coordination number and, for several transition metals, on spin state. Converting an angstrom figure to pm is trivial; matching it against the wrong column of a pm table is the error that actually costs something.
Both units inside one structure table
CIF files and refinement output stay in angstroms while many journals typeset the same distances in picometers, so a single manuscript can carry both. A column of numbers near 1.5 sitting beside a column near 150 is the tell. Check the header before subtracting one geometry from another, because the difference will be nonsense rather than obviously wrong.