The trekking pole grip should rest comfortably in your palm when your arms are bent at a 90-degree angle.
In general, people 5’1″ and under will choose a 100cm pole. Those up to 5’7″ will use a 110-115cm pole. Hikers ranging from 5’8″ to 5’11” need a 120cm pole. And those taller than 6′ will go with the 130cm option.