Fold the rope in half and the reach halves too
On a rappel the rope runs through the anchor and you descend holding both strands, so the distance you can cover is half the rope length. From that you still have to subtract what goes around the anchor, the stopper knots and whatever tail you want to keep in hand. This page takes those two figures off your rope length in turn and shows the reach as a single strand and when doubled, and it also works backwards: type a descent you want to make and it returns the rope length that would be required.
What goes into the numbers
Single-strand reach is the rope length minus the allowance, and the doubled rappel reach is that figure divided by two. The rope needed for a target is the target doubled plus the allowance. How many meters to set aside for knots and tail is not covered by any official standard, so it is not hard-coded and is a value you type in (as of October 2026).
What this page does not do
Diameter-specific uses and the fall counts a manufacturer obtains in testing depend on the product data sheet, so they are not covered. This is length arithmetic only and it does not judge whether a given route is safe. The real distance between anchors and your own judgment on the ground always come first.
Frequently Asked Questions
No official standard exists, so this page does not suggest a figure. Enter what suits the anchor and knots you use and only that value is applied.
No. Diameter-specific uses and fall counts come from manufacturer data sheets, so they are not covered. This page calculates length only.
The rope runs through the anchor and you descend on both strands, so you can only go as far as the folded half, which halves the distance.