How many?

Kilometres

The kilometre, or kilometer in American English, is a unit of length in the metric system, equal to one thousand metres. Many people know a marathon race is 26.2 miles long but did you know that a marathon is 42.195 in kilometres?

Nanometres

The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American spelling) is a unit of length in the metric system, equal to one billionth (short scale) of a metre (0.000000001 m). To demonstrate just how small a nanometre is, it is commonly used to measure atoms and molecules. A typical virus is around 100 nanometres wide. The coronavirus, known as COVID 19 is believed to be between 60 to 120 nanometres wide.