Picometers to Meters (pm to m)

1 picometer equals 1×10⁻¹² meters exactly.

1 picometer = 1×10⁻¹² meters

How to convert picometers to meters

To convert picometers to meters, multiply the number of picometers by 1×10⁻¹². This factor is exact. To go the other way, multiply meters by 1,000,000,000,000.

meters = picometers × 1×10⁻¹²

Example: 10 picometers = 1×10⁻¹¹ meters.

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

Meter (m)

Metric (SI)Current unit

The SI base unit of length. Since 1983 it is defined as the distance light travels in a vacuum in 1/299,792,458 of a second.

Meter comes from the Greek metron, a measure. In 1791 the French National Assembly defined it as one ten-millionth of the distance from the equator to the North Pole along a great circle through Paris, after rejecting the length of a seconds pendulum because that length changes with local gravity. The surveyors Delambre and Méchain measured the meridian arc, and in 1799 a platinum bar known as the Mètre des Archives became the physical standard. NIST notes that this Earth-based meter turned out to be about 0.2 mm shorter than the true pole-to-equator fraction it was meant to represent.

The 1875 Treaty of the Meter created the CGPM and the BIPM to look after common standards, and in 1889 a platinum-iridium prototype bar took over; the original is still kept at the BIPM. In 1960 the meter was tied to 1,650,763.73 wavelengths of an orange-red krypton-86 line, and in 1983 to the speed of light, which made length a quantity derived from the time standard. The 2018 revision reworded that definition without changing the meter's size. NIST offers a handy yardstick for scale: a pace, meaning two steps, is roughly a meter or a yard.

The meter is the reference unit for length on this site.

Sources: BIPM: history of the metre; NIST: the meter and the SI redefinition; Wikipedia: Metre

Related conversions

See all length units.