What Is a Picometer? Definition, Conversions, and Where It's Used in Science
A picometer is 10⁻¹² metres — one trillionth of a metre. Here is how it compares to nm, Å, and µm, and where picometers appear in chemistry and physics.
Read articlePicometer Converter
Convert picometers to nanometers, ångströms, meters, femtometers, micrometers, and more — instantly, with scientific notation and nearest atomic-scale context.
Last updated:
How it works
Enter your value and source unit
Type the number you want to convert and select the unit you are converting from — picometers, nanometers, ångströms, or any of the twelve supported units.
Choose the target unit
Select the unit to convert to — pm, nm, Å, µm, mm, m, km, fm, or inches. The two-step engine routes every conversion through metres for accuracy.
Read the result and context
See the converted value, all-unit equivalents, scientific notation in metres, and the nearest atomic-scale reference so you can picture the size.
How Picometer Conversion Works
The picometer is 10⁻¹² metres — one trillionth of a metre. The “pico” prefix, adopted by the BIPM in 1960, always means 10⁻¹² in the SI system. To convert between any two length units, convert to metres first as the common intermediate, then to the target unit; this two-step method works for any pair of units without needing a direct lookup table. A few relationships are worth memorising: 1 pm = 0.01 Å (so 1 ångström = 100 pm), 1 nm = 1,000 pm, and 1 µm = 1,000,000 pm. The ångström is widely used in chemistry for atomic radii and bond lengths even though it is not an official SI unit, and most bond lengths fall between 74 pm (H–H) and about 250 pm for heavy atoms. Picometers appear wherever the atomic scale matters: atomic radii (50–300 pm), covalent bond lengths (70–250 pm), X-ray wavelengths (10–1,000 pm), and electron-microscopy resolution. The unit is almost never used in everyday measurement but is essential in quantum chemistry, crystallography, and materials science.
Convert A → B:
Step 1: Value (m) = Value × metres_per_A
Step 2: Result = Value (m) ÷ metres_per_B
Key facts:
1 pm = 10⁻¹² m
1 pm = 0.01 Å
1 nm = 1,000 pm
1 µm = 1,000,000 pm
1 m = 1×10¹² pmExample
Convert 154 pm (the C–C bond length) to nm. Step 1: 154 × 10⁻¹² = 1.54×10⁻¹⁰ m. Step 2: 1.54×10⁻¹⁰ ÷ 10⁻⁹ = 0.154 nm. In ångströms: 1.54×10⁻¹⁰ ÷ 10⁻¹⁰ = 1.54 Å. In micrometres: 1.54×10⁻⁴ µm.
Worked examples
| Scenario | Calculation | Result |
|---|---|---|
| Hydrogen atom radius (53 pm) → Å and nm | 53 × 10⁻¹² m ÷ 10⁻¹⁰ (Å); ÷ 10⁻⁹ (nm) | 0.53 Å · 0.053 nm |
| Carbon–carbon bond (154 pm) → nm | 154 × 10⁻¹² = 1.54×10⁻¹⁰ m ÷ 10⁻⁹ | 0.154 nm (1.54 Å) |
| X-ray wavelength (100 pm) → nm | 100 × 10⁻¹² = 1×10⁻¹⁰ m ÷ 10⁻⁹ | 0.1 nm (1 Å) |
| Visible light (500 nm) → pm | 500 × 10⁻⁹ = 5×10⁻⁷ m ÷ 10⁻¹² | 500,000 pm (5,000 Å) |
| DNA helix width (2 nm) → pm | 2 × 10⁻⁹ = 2×10⁻⁹ m ÷ 10⁻¹² | 2,000 pm (20 Å) |
Conversion reference
| Picometers (pm) | Femtometers (fm) | Ångströms (Å) | Nanometers (nm) | Meters (m) |
|---|---|---|---|---|
| 1 | 1,000 | 0.01 | 0.001 | 1×10⁻¹² |
| 10 | 10,000 | 0.1 | 0.01 | 1×10⁻¹¹ |
| 100 | 100,000 | 1 | 0.1 | 1×10⁻¹⁰ |
| 1,000 | 1,000,000 | 10 | 1 | 1×10⁻⁹ |
| 10,000 | 10,000,000 | 100 | 10 | 1×10⁻⁸ |
| 100,000 | 100,000,000 | 1,000 | 100 | 1×10⁻⁷ |
| 1,000,000 | 1,000,000,000 | 10,000 | 1,000 | 1×10⁻⁶ |
| 1×10⁹ | 1×10¹² | 10,000,000 | 1,000,000 | 0.001 |
| 1×10¹² | 1×10¹⁵ | 1×10¹⁰ | 1,000,000,000 | 1 |
Quick facts
- 1 pm = 10⁻¹² m — one trillionth of a metre, an exact definition in the SI system.
- The hydrogen atom radius is about 53 pm, matching the Bohr radius of 52.9 pm.
- 1 ångström = 100 pm = 0.1 nm; the ångström is non-SI but standard in crystallography.
- The shortest common chemical bond, C–H, is about 106 pm.
- Covalent bond lengths span roughly 74 pm (H–H) to 250 pm for heavy atoms.
- Hard X-rays have wavelengths near 10–100 pm, comparable to atomic spacing in crystals.
From the blog
View all →Frequently asked questions
A picometer (pm) is a unit of length equal to 10⁻¹² metres — one trillionth of a metre, or one thousandth of a nanometer. The “pico” prefix means 10⁻¹² in the SI system. Picometers are used to measure atomic radii, chemical bond lengths, and short-wavelength radiation such as X-rays.
There are 1,000 picometers in one nanometer, because a nanometer is 10⁻⁹ m and a picometer is 10⁻¹² m. To convert nanometers to picometers, multiply by 1,000; to go from picometers to nanometers, divide by 1,000.
One metre contains 1×10¹² (one trillion) picometers, since 1 pm = 10⁻¹² m. So 1 m = 1,000,000,000,000 pm. Converting a value in metres to picometers means multiplying by 10¹².
An ångström (Å) equals 100 picometers, or 10⁻¹⁰ m, so 1 pm = 0.01 Å. The picometer is an SI unit, while the ångström is a non-SI unit that remains popular in chemistry and crystallography. A bond length of 1.54 Å is the same as 154 pm.
Picometers measure things at the atomic scale: atomic radii (roughly 50–300 pm), covalent bond lengths (about 70–250 pm), X-ray wavelengths (10–1,000 pm), and the resolution of electron microscopes. They are essential in quantum chemistry, crystallography, and materials science.
Divide the picometer value by 1,000. For example, 154 pm ÷ 1,000 = 0.154 nm. Equivalently, convert to metres first (154 × 10⁻¹² = 1.54×10⁻¹⁰ m), then divide by 10⁻⁹ to reach nanometers.
Most atoms have radii between about 30 and 300 pm. Hydrogen, the smallest, is roughly 53 pm (the Bohr radius is 52.9 pm); carbon is about 77 pm. Whole atoms are therefore typically 1–6 ångströms, or 0.1–0.6 nm, across.
The femtometer (fm) is smaller, at 10⁻¹⁵ m — one thousandth of a picometer. Femtometers are used in nuclear physics to measure atomic nuclei, which are only a few femtometers across. Below that lie the attometer (10⁻¹⁸ m) and smaller SI sub-multiples.