A gate that is too wide will not swing. This calculator tells you the gate width to build or buy, how many hinges and latches you need, and how long the diagonal brace should be.
Your shopping list
How to use the Fence Gate Calculator
- Measure the clear opening between the two gate posts.
- Choose a single gate or a double gate.
- Pick the gate height.
- Read the leaf width, hardware and brace length.
The math behind it
Single gate width = opening – 1.5 in
Double gate leaf width = (opening – 2.5 in) / 2
Hinges = 2 per leaf, or 3 per leaf if taller than 4 ft
Brace = square root of (width squared + frame height squared)
A worked example
What we typed in
- Opening between gate posts: 12 ft
- Gate type: Double gate (two leaves)
- Gate height: 6 ft
What we got
- Width of each gate leaf: 70.75 in
- Hinges in total: 6
- Latches: 1
- Gate leaves: 2
- Diagonal brace length: 96.76 in
- Drop rod or cane bolt: 1
Tips from the job site
- Run the brace from the bottom hinge side up to the top latch side. It stops the gate from sagging.
- Use 6×6 gate posts for any gate over 4 ft wide.
Common questions
Why is the gate narrower than the opening?
It needs a little room to swing and latch. Too tight and it will rub.
How many hinges does a gate need?
Two for a short gate, and three if the gate is over 4 ft tall.
Last checked: (worked example and recalculation).