The name "lead" dates to Roman times, when writing instruments were actually made of lead.

Modern pencils use graphite mixed with clay. Graphite is a form of carbon. When there is a higher percentage of clay in the mixture, the lead is lighter on the page. When there is more graphite, it is darker.

The standard of lead grades is the Hard/Black scale. The higher the H (eg. 6H) the harder the lead, and the ligher it is on the page. The higher the B (eg. 6B) the softer the lead, and the blacker it is on the page. HB is the balance point.

Some brands, such as Blackwing, use their own graphite formulae.