Gate Size Calculator
Calculate recommended gate leaf width and clearances.
Project details
Enter your measurements below.
Start with the clear opening, then subtract the space the hardware needs
A gate leaf should not be made the exact width of the opening between posts. Hinges, latch hardware, movement and installation tolerance need clearance. This calculator works backward from the measured clear opening: subtract the total planned clearance, then divide the remaining width by the number of leaves. The result is a layout target only. Gate frame design, post stiffness, hinge capacity and sag resistance depend on materials and hardware that are outside a width calculation.
Clear opening between finished post faces.
Use the total hinge, latch and center clearance required by the selected hardware/system.
Single and double gates divide the remaining width differently.
How to use the Gate Size Calculator
- Measure the finished clear opening between the surfaces the gate will swing between.
- Determine the total side, hinge, latch and center clearance required by the selected hardware and gate type.
- Subtract that total clearance from the opening.
- Divide the remaining width by one leaf for a single gate or by two for equal double leaves, then verify the hardware's own dimensional requirements.
Why clearance is entered explicitly
Hardware systems vary. By treating clearance as an input, the calculator avoids pretending that one hinge/latch gap is correct for every timber, metal or prefabricated gate.
Use the leaf width to start fabrication planning
Confirm the result against hinge geometry, post position and the gate manufacturer's or fabricator's requirements before cutting the frame.
Worked example: double gate in a 12 ft opening
- Clear opening
- 144 in
- Total planned clearance
- 3 in
- Leaves
- 2
- Available leaf width
- 141 in
141 ÷ 2 = 70.5 inches per equal leaf. That is the geometric target before verifying the actual hinge/latch system and whether the posts can support the chosen gate size.
Practical planning tips
Measure after posts are positioned and plumb when possible; nominal opening dimensions can change during installation.
Add all clearances once. Do not subtract hinge gap in the input and then subtract it again during fabrication.
For double gates, include any center meeting gap or drop-bolt hardware requirement in the total clearance plan.
Large or heavy gate leaves may need different framing, hinges or post design even when the width calculation is correct.
Common mistakes to avoid
Building the leaf exactly equal to the clear opening.
Assuming the same clearance for every hinge and latch system.
Dividing the full opening by two for a double gate before subtracting center/side clearances.
Using the calculated leaf width to infer that the posts or hinges are structurally adequate.
Gate Size Calculator FAQs
How much gate clearance should I use?+
Use the clearance required by the actual hinge, latch and gate system. The calculator intentionally asks for that value rather than prescribing one.
How do I calculate a double gate?+
Subtract all planned clearances from the opening first, then divide the remaining width by two for equal leaves.
Should I measure between post centers?+
No. Use the finished clear opening between the faces that limit the gate movement unless your hardware system specifies another reference.
Does this calculator account for gate sag?+
No. Sag depends on frame construction, leaf weight, hinges, bracing and post stiffness.