Rope Strength Converter
Look up rope breaking strength by diameter and material.
Compare nylon, polyester, polypropylene, and manila rope capacities.
Select a rope material and enter diameter — see breaking strength and working load limit.
Rope Strength
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Rope breaking strength depends on both the diameter and the material of the rope. The breaking strength is the maximum load a new, undamaged rope can hold before it breaks.
Important: Working Load Limit (WLL) Never load a rope to its breaking strength. The Working Load Limit is typically:
- Static loads (no shock): 1/5 of breaking strength (safety factor of 5:1)
- Overhead lifting (people): 1/10 of breaking strength (safety factor of 10:1)
- Dynamic/shock loads: 1/10 or more depending on the application
Approximate breaking strength by material and diameter:
| Diameter | Nylon (3-strand) | Polyester (3-strand) | Polypropylene | Manila |
|---|---|---|---|---|
| 1/4" (6mm) | 1,490 lbs | 1,250 lbs | 1,125 lbs | 540 lbs |
| 3/8" (10mm) | 3,340 lbs | 2,800 lbs | 2,440 lbs | 1,220 lbs |
| 1/2" (12mm) | 5,750 lbs | 4,830 lbs | 3,780 lbs | 2,380 lbs |
| 5/8" (16mm) | 8,600 lbs | 7,200 lbs | 5,600 lbs | 3,960 lbs |
| 3/4" (18mm) | 12,800 lbs | 10,400 lbs | 7,650 lbs | 5,400 lbs |
| 1" (25mm) | 22,200 lbs | 18,000 lbs | 13,200 lbs | 9,000 lbs |
| 1-1/4" (32mm) | 33,800 lbs | 27,500 lbs | 19,800 lbs | 13,500 lbs |
| 1-1/2" (38mm) | 47,800 lbs | 38,800 lbs | 27,000 lbs | 18,500 lbs |
Material characteristics:
- Nylon: Strongest, excellent shock absorption due to stretch (15-30%). Good UV and abrasion resistance. Best for anchor lines, towing, and dynamic loads.
- Polyester (Dacron): Strong with minimal stretch (3-5%). Excellent UV and chemical resistance. Best for halyards, sheets, and fixed-length applications.
- Polypropylene: Lightweight and floats on water. Moderate strength. Poor UV resistance (degrades in sunlight). Good for water ski tow ropes and temporary use.
- Manila (natural fiber): Traditional natural rope. Lower strength and degrades when wet. Good grip and appearance. Used for decorative applications and traditional rigging.
Factors that reduce rope strength:
| Condition | Strength Reduction |
|---|---|
| Knots (any type) | 40-60% reduction |
| Spliced eye | 10-15% reduction |
| UV exposure (aged rope) | 10-50% depending on material and time |
| Wet manila rope | 10-15% reduction |
| Sharp bends over edges | Up to 50% reduction |
| Heat damage | Variable, potentially catastrophic |
Practical tips:
- Inspect rope regularly for fraying, glazing, stiffness, or discoloration. Replace damaged rope immediately.
- Store rope in a cool, dry, dark location to maximize lifespan.
- Never exceed the Working Load Limit, especially for overhead or life-safety applications.
- When in doubt, use a thicker rope or a stronger material.