How to measure your boot opening (and why it often decides the fit)

Updated 4 November 2026 · 5 min read

A box can fit comfortably inside a boot and still be impossible to load, because it won't get through the hole. Boot openings are shaped around tail lights, hinges, seals and the bumper, and on many cars the aperture is noticeably smaller than the load space behind it. This guide shows you how to measure the opening properly so the car boot fit calculator can check it separately from the interior.

Why the opening is checked separately

When you slide a box into a boot, the end of the box (its cross-section) has to pass through the opening first. A box 120 cm long, 60 cm wide and 40 cm tall, loaded lengthways, only needs an opening of about 60 × 40 cm, even though the box is 120 cm long. Turn the same box on its side and it needs 40 × 60 cm. Stand it upright and the opening has to be at least 60 cm wide and 120 cm tall, which few cars offer.

That's why our engine tests each orientation twice: once against the interior (length, width, height) and once against the opening for a straight-through push. If an item only fits the interior when rotated in a way the opening won't allow, the result won't say "likely fits".

Measuring opening width

1. Open the boot or tailgate fully. On a powered tailgate, check it opens to its maximum height setting.
2. Find the narrowest horizontal gap between the left and right sides of the opening. It's usually between the tail-light housings, the rubber door seals or the plastic side trims.
3. Measure at three heights: just above the loading lip, halfway up, and near the top. Write all three down.
4. For a straight-through check, use the width at the height where the widest part of your item will pass. For a box this is usually the full height of the box above the lip, so use the narrowest width within that band.

Measuring opening height

1. Find the top of the loading lip, the edge the item will slide over. That's often the bumper or a metal sill, not the boot floor.
2. Find the lowest point of the open tailgate or boot lid aperture directly above it. Look for the latch striker, the rubber seal, the tailgate's lower edge or a light bar.
3. Measure vertically between those two points, near the centre and again near each side. The centre is often taller, while the corners are cut by curved trim.
4. Record the smallest value within the width your item will use.

Things that steal space from the opening

• Seals: rubber seals compress a little, but don't count on squashing them. They damage easily, and you'll get water leaks.
• Latches and strikers: the metal latch loop in the middle of the sill often sticks up a centimetre or two. Boxes catch on it.
• Trim and tail lights: plastic trim panels are easy to scratch or crack. Measure to the trim, not to the metal behind it.
• Tailgate hardware: gas struts, wiper motors and handles can hang down into the aperture on some cars.
• Saloon (sedan) boot lids: on many saloons the hinge arms swing down into the boot as the lid closes. Treat the space they sweep through as unusable. Anything sitting there gets crushed or stops the lid closing.

The loading lip

The loading lip is the sill you lift items over. Two things matter:

• Lip height above the boot floor. If the floor sits lower than the sill, the item has to come in high and then drop. For a long box, the lip limits how steeply you can tilt it. For heavy items it means a bigger lift.
• Lip height above the ground. This is a lifting question rather than a fit question, but it's worth knowing for heavy boxes. You may need two people.

For opening height, measure from the top of the lip, not from the boot floor. The item has to clear the lip on its way in.

A worked example

Take a hypothetical estate (wagon) whose opening measures 102 cm wide at lip level, 96 cm halfway up and 88 cm near the top, with an opening height of 70 cm. You want to load a hypothetical flat-pack box of 180 × 92 × 12 cm.

• Laid flat, pushed in lengthways: the box presents a 92 × 12 cm end. It only uses the bottom 12 cm of the opening, where the width is about 102 cm. With 2 cm of clearance it needs 94 × 14 cm. It passes.
• On its edge, pushed in lengthways: it presents a 12 × 92 cm end. That needs 94 cm of opening height, and the opening is only 70 cm. It fails.

So the opening allows the flat orientation only. The interior then has to accept a box lying flat: 180 cm of length (almost certainly seats down) and 92 cm of width between the wheel arches. That's the next thing to check.

Common mistakes

• Measuring opening height from the boot floor instead of the top of the loading lip.
• Measuring width only at the bottom, where the opening is widest.
• Assuming the opening is the same size as the interior.
• Forgetting the latch striker, which catches the underside of boxes.
• Measuring with a powered tailgate set to a reduced opening height.

Related reading

For the full set of interior measurements see how to measure your car boot. To understand why the arches often limit width once the item is inside, read understanding wheel arch width.