Picometers to Kilometers (pm to km)

1 picometer equals 1×10⁻¹⁵ kilometers exactly.

1 picometer = 1×10⁻¹⁵ kilometers

How to convert picometers to kilometers

To convert picometers to kilometers, multiply the number of picometers by 1×10⁻¹⁵. This factor is exact. To go the other way, multiply kilometers by 1×10¹⁵.

kilometers = picometers × 1×10⁻¹⁵

Example: 10 picometers = 1×10⁻¹⁴ kilometers.

About these units

Picometer (pm)

Metric (SI)Current unit

One trillionth of a meter. Atomic diameters are typically a few hundred pm.

One trillionth of a meter, the picometer (pm) is the SI length that sits below the nanometer and above the femtometer. It equals 0.01 angstrom, so a figure in angstroms converts by multiplying by 100. Wikipedia notes that the symbol mu-mu was once used for it, and the NIST list of SI prefixes gives pico as 10 to the power of minus 12.

In practice the unit belongs to chemistry and atomic physics, where distances between bonded atoms are expressed as a few hundred of them. A carbon to carbon single bond is about 154 pm long, and a helium atom is estimated at about 62 pm across, while atoms in general run from roughly 62 to 520 pm in diameter. Chemists who grew up with the angstrom increasingly quote the same distances in picometers, because the angstrom is no longer part of the SI. Gravitational-wave work pushes the scale further: the planned LISA detector is expected to resolve displacements of about 20 pm over a 2.5 million kilometer baseline.

1 picometer = 1×10⁻¹² meters (exactly).

Sources: Wikipedia: Picometre; NIST: metric (SI) prefixes; Wikipedia: Angstrom

Kilometer (km)

Metric (SI)Current unit

1,000 meters. The standard unit for road distances in most countries.

A name for 1,000 meters took a while to settle. In 1793 France's National Convention made the metre the sole French unit of length, and the first proposed name for the thousand-metre multiple was millaire. Everyday French usage then leaned on the myriametre, 10,000 meters, well into the 1800s. The Netherlands adopted the kilometre in 1817, under the local name mijl, and made it the only official unit of that size in 1867. In 1935 the CIPM dropped the myria- prefix, which left the kilometre as the standard unit for road-scale distances.

Kilo- is the SI prefix for a thousand, and the kilometre is now the preferred unit for land distances in most of the world, with the United States, the United Kingdom and Liberia among those that still use the mile. One kilometre is about 0.621 mile. The main span of Lisbon's 25 de Abril Bridge, at 1.013 km, gives a sense of the scale. Even its pronunciation has been argued over: in 1970 Australia's Metric Conversion Board made stress on the first syllable official, although Prime Minister Gough Whitlam argued for stress on the second. Military slang in several countries calls it a klick.

1 kilometer = 1,000 meters (exactly).

Sources: Wikipedia: Kilometre; Wikipedia: Metric prefix; BIPM: history of the metre

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