Addendum

Addendum, abbreviated as A, is the radial distance of a tooth from the pitch circle to the top of the tooth.

 

Addendum formula
\(\large{ A = \frac{1}{DP} }\)
Symbol	English	Metric
\(\large{ A }\) = addendum	\(\large{in}\)	\(\large{mm}\)
\(\large{ DP }\) = dimetrical pitch	\(\large{in}\)	\(\large{mm}\)