Traditional Skis
Traditional cross country skis are usually longer and thinner, and used in pre-cut tracks at Nordic resorts. Size them by taking your height in inches, multiplying by 2.6, and adding 25 inches to get a number. This number equates to the length in centimeters that you should choose.
Skate Skis
Skate skis are shorter for greater maneuverability in the aggressive skate stride. Multiply your height in inches by 2.6, then add 15 inches to get a number in centimeters for your ski length.
Traditional Poles
Traditional poles should be sized so they come to rest approximately under your armpits.
Skate Poles
Skate skiers use their poles more aggressively and prefer slightly longer poles. Skate poles are usually sized so they reach the skier's nose, but some skiers get poles shorter, approximately to chin or lip height.
Weight
A skier's weight can affect the length of ski that works best. Heavier skiers may require longer skis to provide better flotation in the snow, while lighter skiers can round down a little and choose shorter skis that provide a little more maneuverability.