Rope Length Calculator
Enter a pitch's depth and rigging plan to get the rope you actually need to carry — not just the drop itself, but the rigging, the tail, and a safety margin on top.
Rope you need
How the estimate is built
The base length is the pitch depth plus a top rigging allowance, a bottom tail allowance, and an allowance for each rebelay or deviation along the way. A safety margin percentage is then applied to the whole base length, since real anchors, ledges, and rub points rarely match a tape measure exactly.
The final recommendation rounds that figure up to the nearest rope increment — 5m by default — so you get a length that matches how rope is actually bought, cut, and marked, with a small buffer rather than coming up short at the bottom of the drop.
Frequently Asked Questions
Why is the recommended rope longer than the pitch depth?
The rope has to do more than just span the drop. You need extra length to tie off and rig the top anchor, a tail past the bottom stopper knot so the end isn't right at your feet, and — if the pitch has a rebelay or deviation — extra rope consumed re-anchoring partway down. A safety margin on top covers measurement error and an anchor placed a little further back than expected.
What is a rebelay and why does it eat rope?
A rebelay is a fresh anchor partway down a pitch, usually added to keep the rope off a rub point or a waterfall. Rigging it means tying off the rope at that anchor and starting a new hang below, which consumes a few metres in knots and wraps compared to a single unbroken hang — this tool adds a configurable allowance per rebelay for that.
Why round up to a 5m increment?
Rope is usually bought, cut, and marked in round lengths — 20m, 25m, 40m, and so on — so a recommendation of, say, 40.7m isn't something you can buy or mark exactly. Rounding up to the nearest 5m gives you a real length to buy or pull from the rope bag, with a little extra rather than a little short.
Does this account for rope stretch or diameter?
No — it's a length estimate based on the geometry of the pitch, not a rope's stretch or elongation under load. Static caving rope stretches only a little in normal use, but always check the specific rope's spec sheet and inspect it before a trip; this tool doesn't replace that check.
Planning estimate only. Rigging a pitch safely takes trained judgment on the day — confirm anchors, rope length, and technique with a qualified leader or your caving club before you rig.