What is standard length? I have been using 135cm poles for (what seems like) ever.
Use the 90deg elbow rule. Pole upside down with handle resting on the ground, hand holding the pole under the basket (handle side of basket), stand so your upper arm is parallel to your torso, and your forearm should be parallel to the ground if you chose the right length. This works for 98% skiers. If you race, take into account that your ski base to boot sole is 55mm and boot sole to heel is 50mm.