Route From the guidebook or measured

Height from the Ground to the Top of the Route m

The pitch length, measured along the route if it wanders, not straight up.

Anchor Set Back from the Top m

Extra rope to reach an anchor back from the edge; zero for bolts at the top.

Rope in the Knot and at the Belay m

Safety Margin %

Spare for stretch, a wandering line and guidebook heights that are out.

Rope From the rope label

Rope Length m

As marked; a rope that has had a damaged end cut off is shorter.

Rope Weight g/m

Rope Needed with the Margin

— m

Twice the height plus setback, plus the knot and belay, plus the margin

Rope Check

Rope Needed without Margin: — m
Rope Left Over (Negative = Too Short): — m
Longest Route This Rope Serves: — m
Rope for a Single-Strand Line to the Anchor: — m
Rope Mass: — kg

Lowering a climber from the anchor and abseiling on a doubled rope both use the route twice: up to the anchor and back down to the ground. Height, setback, allowance and margin are yours; guidebook heights are often rounded and lines wander, which is what the margin is for. The single-strand figure is for a line fixed at the anchor and hanging to the ground. Stretch under load is not added separately. **Always tie a stopper knot in the free end of the rope, or close the system, whatever this tool says: a rope that is too short drops the climber off its end.**

Climbing Rope Length for a Route: Lowering or Abseil, Safety Margin, Longest Route & Rope Mass — free, with the formula and a worked example, at Textile School.