CALCULATOR
Rope Strength Calculator
Estimate the breaking strength and safe working load of a line from its fibre and diameter, with the safety factor you choose applied explicitly.
What this gives you
Inputs: Fibre, diameter, safety factor, load type. Outputs: Breaking strength, WLL, safety factor, recommended diameter, elongation. A safety factor below 5 is not recommended for any load-bearing application. Dynamic loading needs an additional derate on top of the static factor.
Working load limit
—
Breaking strength—
Safety factor—
Suggested diameter—
Stretch at load—
Dry breaking strength—
MBL = k × d²WLL = MBL ÷ (safety factor × dynamic factor)d_required = √(target × factor ÷ k)
∞ RELATED
Put the number to work
Free tool
Knot Strength Calculator
Line breaking strength→Strength at the knot
What a knot costs you, and what the line can safely hold once it is tied.
Calculator
Free tool
Rigging Load Calculator
Load weight→Tension per leg
Sling tension against angle — and why a wide angle multiplies the load so fast.
Calculator
INTERACTIVE
3D Studio
See the same numbers as geometry — a rope under load, a splice worked tuck by tuck, force vectors on a rig.
3D Studio
These calculators use simplified models and typical catalogue values. They are for planning and
teaching, not for certifying a lift. Real capacity depends on the specific product, its condition,
the load path and the environment. Where a manufacturer’s rating or a regulation gives a
different figure, that figure governs.