Gate Calculator: Leaf Width, Brace Length and Angle, Weight and Hinge Pull

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Opens on the book's own fence. Change any number to your own and press Calculate.

Start from fills the boxes below

Opening between the posts mm, clear

Gap each side mm, hinge and latch

The frame and brace

Rail width mm (2x4 = 89)

Rail thickness mm

Rails

Rails the brace runs between mm, center to center

Braces

Pickets or boards, and the hinges

Pickets or boards

Width mm

Thickness mm

Length mm

Hinge spacing mm, top to bottom

Wood density kg/m³ (dry pine; wet is heavier)

Someone on the latch end kg, optional

Ground rises across the swing %

Gap under the gate mm

Enter the opening and press Calculate.

The formula

Leaf = opening − hinge gap − latch gap
Brace = √((leaf − rail width)² + (rail spacing − rail width)²); angle = arctan(rise ÷ run)
Weight = volume of wood × density (569 kg/m³ for dry pine)
Pull on the top hinge = W × d ÷ h (weight × distance to its middle ÷ hinge spacing)

The book's worked example, Chapter 8. A 1,000 mm opening with 10 mm each side leaves a 980 mm leaf. Route A's brace runs 891 mm across and 561 mm up: 1,052.9 mm at 32.2°. The gate weighs 13.88 kg, and with hinges 650 mm apart the top one is pulled with 104.7 N. Route B's heavier gate (25.5 kg, two braces of 1,034.4 mm) pulls only 101.8 N, because its hinges are 1,228.8 mm apart.

Check the frame square by its diagonals before the boards go on: equal diagonals, square frame. An anti-sag cable runs the other way, in tension, from the top hinge corner to the bottom latch corner. Prices are illustrative US home-center prices from October 2026, shown without a currency sign; put in your own. Everything stays in your browser: no sign-up, nothing stored.