Gate Brace Calculator

About this calculator

A wooden or metal gate racks — sags diagonally out of square — under its own weight unless a diagonal brace resists that shear. The brace's required length is pure geometry: for a gate of width w and height h, the diagonal follows the Pythagorean theorem, brace length = √(w² + h²), running from the low corner at the hinge side to the high corner at the latch side.

Fencing and carpentry guides also track the resulting brace angle from horizontal, since it affects how the brace transfers compressive load down to the hinge post — a properly oriented diagonal brace (compression, not tension) is what keeps a wide gate from drooping at the latch end over time, which is why it is standard practice on any gate wider than about 4 feet.