What is a safe weight ratio for belaying?

A weight ratio of 1.4:1 or less (climber to belayer) is generally considered safe for standard belaying without a ground anchor. Above this ratio, the belayer may be pulled off the ground or struggle to hold a fall. An assisted braking device like a GriGri can help compensate for larger weight differences.

What is an assisted braking device?

An assisted braking device (such as a Petzl GriGri) uses a camming mechanism that automatically locks the rope when loaded quickly, as in a fall. This provides significantly more friction than a standard tubular device, making it safer especially for sport climbing and when there is a large weight difference.

When do I need a ground anchor?

A ground anchor is recommended when the climber outweighs the belayer by more than 40% (ratio above 1.4:1). This prevents the belayer from being pulled upward or into the wall during a fall, which could cause them to lose control of the rope.

How does rope diameter affect belaying?

Thinner ropes (under 9.5mm) generate less friction in belay devices, making them harder to hold. Thicker ropes (10mm+) provide more friction. Always check your belay device manufacturer specifications for supported rope diameter ranges.

CampCalcs

Belay Calculator

Calculate belay forces, friction and holding power for different belay devices and weight combinations.

Climber Weight

Belayer Weight

Belay Device

Rope Diameter

How We Calculate This

This calculator estimates belay forces and determines whether a ground anchor is needed based on the weight difference between climber and belayer.

Weight ratio

Weight ratio = Climber weight / Belayer weight

Friction multipliers

Tubular device: ~2.5x friction
Assisted braking: ~5.0x friction
Figure-8: ~1.8x friction
Plate: ~2.2x friction

A ground anchor is recommended when the weight ratio exceeds 1.4:1.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify conditions and use proper safety equipment outdoors.