# parts per billion

Auxiliary unit of measure
Unit name parts per billion
Unit symbol ${\ displaystyle \ mathrm {ppb}}$
Formula symbol ${\ displaystyle {\ mathit {p}}}$
Type quotient
definition ${\ displaystyle \ mathrm {1 \, ppb = 1 \, \ cdot 10 ^ {- 9} = 0 {,} 000 \, 000 \, 001}}$
Named after English parts per billion , "parts per billion"

The English expression parts per billion ( ppb , in German "parts per billion") stands for the number 10 −9 (one billionth) and is sometimes used in connection with relative quantities, i.e. for the specification of those salary values that are proportions.

Since the word billion can mean a billion or a trillion depending on the use of the long or short scale (see long and short scales ), the IEC 1978 recommended that the terms ppt, ppm and ppb not be used. The international ISO standard has followed this view .

## conversion

• 1 ppb = 10 −3 ppm
• 1 ppb = 10 −9

## Mixing ratios (ppbv, ppbw)

In addition, the following variants are occasionally used in the literature:

• ppbv parts per billion by volume (volume mixing ratios), corresponds to 10 −7 % by volume
• ppbw parts per billion by weight (weight mixing ratios), corresponds to 10 −7 % by weight

## use

The term ppb is often used in microelectronics , for example when specifying a doping or impurity concentration , when characterizing the inaccuracy of time standards , and in chemical and environmental concentration and trace analysis .