Fence gate width & post calculator
Size a gate opening and its hardware: rough opening width, the two heavier gate posts, and the hinge, latch and drop-rod count.
Calculator
A single gate with 1 × 48" leaf needs a 49.0" rough opening, 2 heavier gate posts, 2 hinges and a latch. Gate posts are set deeper and counted separately from line posts.
A gate is a small run with its own rules. The rough opening — the clear gap you frame between the gate posts — is the leaf (or two leaves) plus the hinge-side and latch-side gaps that let it swing and latch without binding. A 4 ft walk gate is one 48" leaf plus about an inch of gaps, so a 49" rough opening.
Gate posts are always heavier and set deeper than line posts because they carry the swinging weight and take the slam of the latch. Every gate uses two of them, sized up (6×6 is common where line posts are 4×4). Hardware scales with the gate: 2–3 hinges per leaf, one latch, and a drop rod (cane bolt) for a double drive gate so one leaf stays fixed while the other swings.
Set the gate posts with plenty of concrete — size it with the concrete-per-post calculator at the larger post width — and count them separately from the line posts in the fence post calculator.
Formula
rough_opening = leaf_width_in × leaves + hinge_gap_in + latch_gap_in\ngate_posts = 2 (heavier, set deeper than line posts)\nhinges = hinges_per_leaf × leaves\nlatch = 1 (+ 1 drop rod for a double gate)
Worked example
A 4 ft single walk gate, 0.5" gaps each side, 2 hinges:
- rough opening = 48 × 1 + 0.5 + 0.5 = 49"
- gate posts = 2 (heavier than line posts)
- hardware = 2 hinges + 1 latch
A 10 ft double drive gate is two 5 ft leaves plus a drop rod.