Metric SI Prefixes Chart

In order to avoid large or small numerical values, decimal multiples and submultiples of the coherent SI units are formed with the SI prefixes.

SI Prefixes
Factor Prefix   Factor Prefix
Name Symbol Name Symbol
1024 yotta Y 10-1 deci d
1021 zetta Z 10-2 centi c
1018 exa E      
1015 peta P 10-3 milli m
      10-6 micro µ
1012 tera T 10-9 nano n
109 giga G 10-12 pico p
106 mega M      
103 kilo k 10-15 femto f
      10-18 atto a
102 hecto h 10-21 zepto z
101 deca da 10-24 yocto y

The symbol of a prefix is considered to be combined with the single unit symbol to which it is directly attached, forming with it a new symbol for a decimal multiple or submultiple that can be raised to a positive or negative power and that can be combined with other unit symbols to form symbols for compound units.

1 cm3 = (10-2m)3 = 10-6 m3



  • ISO 80000-1 : 2009, Quantities and Units —— Part 1: General