The most common reason a custom gate does not fit is a measurement taken in one spot, on the wrong reference points, without allowing for hinges and gaps. This guide shows you exactly what to measure, where, and how much clearance to leave, so the gate you order fits the opening you actually have.

Measure the opening, not the gate you imagine

Your job is to record the true space between the two fixed points the gate will attach to. That means the finished posts or pillars, at their closest faces. Do not measure to the fence, the wall render, or a temporary marker. Measure to the exact surfaces the hinges and latch will mount on.

Width: measure in three places

Openings are rarely perfectly parallel. Measure the gap at the top, middle, and bottom between the two posts. Use the smallest of the three as your working width. If the difference between them is more than 1 to 2 cm, the posts are out of plumb and should be corrected before the gate is made.

Height: measure both sides

Measure from the ground to the top of each post, on both sides. Note ground slope across the opening. If one side is lower, the gate maker needs to know so the bottom rail can follow the ground or clear it evenly.

Clearances you must subtract

A gate cannot be the exact width of the opening, or it will bind. You subtract clearances for the hinge gap, the latch gap, and ground clearance. Typical practical allowances:

These are common starting points, not fixed rules. Your gate maker will confirm exact figures based on the hinge type and whether the gate is manual or automated. Always agree the clearances with them before fabrication.

A real scenario

A customer measured a driveway opening once, across the middle, and ordered a 4-meter gate. On install day the gate would not close: the pillars leaned inward at the top by 3 cm, and the ground rose 6 cm on the latch side. The gate had to be re-cut and the bottom rail re-angled. A three-point width measurement and a note about the slope would have caught both problems on paper. Ten minutes of careful measuring would have saved a week of rework.

Common mistakes and how to fix them

Measuring once. A single reading hides out-of-square posts. Fix: always take top, middle, and bottom, both for width and height.

Measuring before the posts are finished. Render, cladding, or paint changes the gap. Fix: measure only after posts and pillars are in their final finished state.

Forgetting the swing path. A gate that fits the gap can still hit the ground on a slope. Fix: check the arc for swing gates by swinging a string or plank through the path.

Not allowing for automation. Motors need mounting room and specific hinge positions. Fix: tell the maker before measuring if a motor is coming.

Using a soft tape over a long span. Tapes sag on wide openings. Fix: pull the tape tight and level, or use a laser measure for spans over 3 meters.

Step-by-step checklist

• Confirm posts and pillars are in their final, finished condition.
• Measure width at top, middle, and bottom; record the smallest.
• Measure height on both sides from ground to post top.
• Note any ground slope across the opening in centimeters.
• Photograph both posts and the full opening for the maker.
• State whether the gate is manual or will be automated.
• Agree hinge, latch, and ground clearances in writing before fabrication.

Conclusion

Accurate gate measurement is not hard, but it is unforgiving of shortcuts. Measure the finished posts in three places, record the slope, and agree clearances before anything is cut. Your next step: take the seven readings on the checklist above and share them, with photos, when you request your quote.

FAQ

Should I measure the opening or tell the maker my desired gate size?

Give the maker the opening measurements and let them calculate the gate size. They subtract the correct clearances for the hinges and latch you choose.

How much ground clearance is right?

Commonly 50 to 100 mm, more if your ground slopes or floods. The goal is to clear debris and movement without leaving a gap a pet or child could pass through.

My posts are slightly out of plumb. Can the gate still fit?

Minor errors can be absorbed with hinge adjustment, but larger lean should be corrected first. Tell the maker the exact difference between your top and bottom readings.

Do I measure differently for a sliding gate?

Yes. A sliding gate needs the opening width plus clear side room equal to the gate width for it to roll open. Measure that side run as well.