Femto-

This article describes the SI prefix. For the manga character, see Griffith (Berserk).

Femto- (symbol f) is a prefix in the metric system denoting a factor of 10⁻¹⁵ or 0.000000000000001. Adopted by the 11th Conférence Générale des Poids et Mesures, it was added in 1964 to the SI. It is derived from the Danish word femten, meaning "fifteen".

Example of use:

• a proton has a diameter of about 1.6 to 1.7 femtometres.

The femtometre shares the unit symbol (fm) with the older non-SI unit fermi, to which it is equivalent. The fermi, named in honour of Enrico Fermi, is often encountered in nuclear physics.

SI prefixes

Prefix	Symbol	1000m	10n	Decimal	Short scale	Long scale	Since
yotta	Y	10008	1024	1000000000000000000000000	Septillion	Quadrillion	1991
zetta	Z	10007	1021	1000000000000000000000	Sextillion	Trilliard	1991
exa	E	10006	1018	1000000000000000000	Quintillion	Trillion	1975
peta	P	10005	1015	1000000000000000	Quadrillion	Billiard	1975
tera	T	10004	1012	1000000000000	Trillion	Billion	1960
giga	G	10003	109	1000000000	Billion	Milliard	1960
mega	M	10002	106	1000000	Million		1960
kilo	k	10001	103	1000	Thousand		1795
hecto	h	10002/3	102	100	Hundred		1795
deca	da	10001/3	101	10	Ten		1795
		10000	100	1	One		–
deci	d	1000−1/3	10−1	0.1	Tenth		1795
centi	c	1000−2/3	10−2	0.01	Hundredth		1795
milli	m	1000−1	10−3	0.001	Thousandth		1795
micro	μ	1000−2	10−6	0.000001	Millionth		1960
nano	n	1000−3	10−9	0.000000001	Billionth	Milliardth	1960
pico	p	1000−4	10−12	0.000000000001	Trillionth	Billionth	1960
femto	f	1000−5	10−15	0.000000000000001	Quadrillionth	Billiardth	1964
atto	a	1000−6	10−18	0.000000000000000001	Quintillionth	Trillionth	1964
zepto	z	1000−7	10−21	0.000000000000000000001	Sextillionth	Trilliardth	1991
yocto	y	1000−8	10−24	0.000000000000000000000001	Septillionth	Quadrillionth	1991

External links

• Bureau International des Poids et Mesures (BIPM)