How to measure a gate or garage opening before you ask for a quote
Mount Everest Automatic Doors team6 min readUpdated
Before you ask for a quote on a new gate, garage door or shutter, a few measurements help. We always measure properly at the site visit, so yours do not have to be perfect. They do need to be honest. This guide explains what to measure, how and in what order, so that a first conversation is informed.
What you need
A tape measure of at least five metres, a pen and paper or a notes app on your phone, a spirit level if you have one and a helper for wide openings. Work in millimetres or centimetres and say which in your notes. A steel tape is better than a cloth tape because it does not stretch.
Why one measurement is not enough
Walls lean, floors slope and old openings go out of square. A width measured at the top can differ from the width at the floor. Doors and gates are made to the smallest dimension, so the smallest figure is the one that matters. That is why we measure at several points.
Step 1: the width
Measure the clear width between the finished surfaces on each side, at three heights: near the floor, in the middle and near the top. Write all three. Use the smallest as your working width. If the opening has pillars or a frame, measure between the inner faces, not the outer. If there is a plinth or a kerb at the floor, measure above it.
Step 2: the height
Measure from the finished floor to the underside of the lintel or the soffit, at the left, in the centre and at the right. Write all three. Use the smallest as your working height. If the floor slopes, note the slope and measure from the highest point of the floor in the opening, because a door must clear it.
Step 3: the headroom
Headroom is the clear space above the opening, up to the ceiling or the first obstruction. For a sectional garage door, the tracks and springs need space there. For a rolling shutter, a box needs space. Measure from the top of the opening to the ceiling, and note anything in the way, such as a beam, a pipe or a light fitting.
Step 4: the side room
Side room is the clear wall on each side of the opening, measured along the wall. A sectional door needs some for the track brackets. A sliding gate needs a long run beside the opening. Measure from each side of the opening to the nearest obstruction, such as a corner, a tree or a drain.
Step 5: the depth behind
For a garage, measure from the opening back into the garage: the clear distance before you reach the rear wall or any obstruction. Sectional doors need a certain run inside when they are open. For a gate, measure the clear space behind the opening for a swing arc or a sliding path.
Step 6: the ground
Look at the ground along the line where the gate or door will operate. Is it level? Does it slope toward or away from the opening? Is there a drain, a kerb or a change of surface? Take a photo along the line. A level and a short length of straight timber laid on the ground help you see a slope.
Step 7: the structure
Note what the opening is built from. Concrete, block, steel, aluminium and timber all take fixings differently. Note whether pillars look sound, whether there are cracks and whether the lintel appears strong. You are not judging; you are describing. We judge at the visit.
Step 8: power and access
Find the nearest power point or distribution board and measure roughly how far it is from the place a motor or opener would sit. Note whether there is already a cable route. For gates, note the route cable could take across the ground. For a garage door, note where the opener would go and whether there is a socket on the ceiling.
Step 9: write it down
Make a simple sketch of the opening. Draw a rectangle, label the width figures along the top and bottom and the height figures along the sides. Mark headroom, side room and depth. Add a short list of things in the way. A sketch, even rough, is more useful than a list of numbers.
Step 10: take the photos
Photograph the opening from outside and inside, with the tape in frame. See our guide on photographing a door or gate for the full list.
Common mistakes
- Measuring the old door, not the opening. The old door may not match the opening.
- Measuring once. Check each measurement twice.
- Using the largest figure. Use the smallest.
- Ignoring the floor. A slope or a step changes what fits.
- Forgetting headroom and side room. A door that fits the opening may not fit the space around it.
- Mixing units. Say millimetres or centimetres.
What happens to your numbers
We use your figures to guide the first conversation, the likely door type and the questions to ask. At the site visit, a technician checks and measures. If they differ, the technician's figures are used for the order, and we tell you. We never order equipment from a customer's measurements alone.
When to ask for help
If the opening is very wide, very high, curved or irregular, or if you cannot reach the top safely, do not climb on a ladder alone. Send photos and we measure at the visit. Never stand on a gate, a door or an unstable surface to measure.