The Union Internationale des Associations d’Alpinisme (UIAA) is the international mountaineering and climbing federation that creates safety standards to which all climbing ropes must adhere. Independent labs are responsible for carrying out the tests. All dynamic ropes carried by REI pass the UIAA tests.

The packaging on dynamic climbing ropes lists the test results for UIAA safety standards, including fall rating, static elongation, dynamic elongation and impact force. Looking at these ratings while thinking about what type of climbing you will be doing can help you choose a rope.

The UIAA tests ropes to see how many falls they can hold before failing. Lab falls create much greater force than most real-world climbing falls. Therefore, the fall rating is mostly a comparative value.

Single ropes are tested by dropping an 80kg weight onto the rope, half ropes are tested by dropping a 55kg weight on a single strand, and twin ropes are tested by dropping an 80kg weight on 2 strands. All single ropes and half ropes must withstand a minimum of 5 UIAA falls. Twin ropes must withstand a minimum of 12 UIAA falls.

All ropes that meet the UIAA fall rating standard are safe for climbing. A rope with a higher fall rating may mean that that rope will last longer than a rope with a lower rating. However, always inspect your rope closely after a severe fall and consider retiring it if any damage is detected.

Static elongation, also called working elongation, is the amount that a dynamic rope stretches with an 80kg weight hanging from it. Elongation on single and twin ropes cannot exceed 10 percent of the total rope length and half ropes cannot exceed 12 percent.

Static elongation is important to consider when top-rope climbing, hauling gear and climbing fixed ropes with ascenders. Higher static elongation generally indicates less efficiency because energy is wasted through rope stretch.

Dynamic elongation is the distance the rope stretches during the first UIAA fall. Higher elongation equals a longer fall, so generally speaking, a lower number is better because less stretch may prevent a falling climber from hitting a ledge or the ground. However, less dynamic elongation means a higher impact force on the climber, belayer and gear. The UIAA allows ropes to stretch no more than 40 percent of the length of the entire rope. 

Impact force is the amount of force in kilonewtons that is put on the falling weight during the first UIAA fall. A lower number indicates less force on the falling climber, the belayer and the gear. The higher the dynamic elongation, the lower the impact force.

Lower impact forces make for a soft landing on the rope when you fall, but with that usually comes greater stretch, which can be less efficient when top roping.