Free tool
Rigging Load Calculator
Estimate a log’s weight from species, diameter and length, see how a drop multiplies the load, and get a minimum rope and sling strength with a working-load margin.
Estimate only, using typical green weights and a simple elastic rope model with no friction or rope running. Real loads depend on the rope, the rigging point, friction and technique. When in doubt, take smaller pieces.
Rigging gear for the job
How the numbers are worked out
Log weight is the volume of a cylinder (π × radius² × length) multiplied by the green weight of the species per cubic foot. Green wood is heavy: a 20-inch red oak round 4 feet long weighs roughly 550 pounds before it ever moves.
When a piece is allowed to free-fall before the rope catches it, the force on the system can be several times the static weight. The calculator uses a simple fall-factor based multiplier to show how quickly that adds up, then applies a 10:1 design factor, which is the margin commonly used for arborist rigging rope working load limits.
Use it as a sanity check, not a certificate
Real shock loads depend on rope stretch, friction on the lowering device, how the piece swings and the rigging point itself, which is often the weakest link. Treat the result as a starting point for a conversation with your crew, keep drops short, let the rope run, and when the numbers look big, take smaller pieces.
Common questions
How much does green oak weigh?
Red oak runs around 63 pounds per cubic foot green and white oak is about the same. Our calculator uses typical green weights for each species and shows the figure it used.
What is a 10:1 design factor?
It means the working load you plan to put on rope is no more than a tenth of its rated breaking strength, to allow for wear, knots, bends and shock loading.