The number that decides whether a sofa gets into your home is not its width or even its depth on its own, it is the diagonal depth, the distance from the bottom front corner to the top back corner once the sofa is tilted onto its side for carrying. A standard UK internal door, built to BS 4787, has a leaf width of 762mm and a clear opening once the frame is fitted that usually comes out closer to 686mm to 720mm. Removing the door from its hinges and taking off the stops typically recovers another 40mm to 50mm, which is often the exact margin that turns a failed delivery into a successful one.

Working out diagonal depth properly

The formula is simple once you have the sofa's depth and height. Square the depth, square the height, add the two numbers together, then take the square root. Using Kukuu's own Chesterfield two seater as a real example, with a depth of 94cm and a height of 75cm, the sum comes to 8836 plus 5625, which is 14461, and the square root of that is roughly 120cm. That 120cm figure is the sofa's diagonal depth, and it is the number you compare against a doorway's own diagonal, not against the door's flat width alone.

A standard UK doorway, 720mm clear and 1981mm tall, has its own diagonal of roughly 211cm once you run the same calculation against the door opening itself. Since the sofa's diagonal depth of 120cm is well under that 211cm figure, a two seater Chesterfield tilted correctly will clear a standard UK doorway without needing the door removed, though a tight 90 degree turn in a hallway is a separate calculation entirely and the one most buyers forget to check.

The insight most sofa guides miss

Here is something worth knowing before you assume a bigger sofa automatically means a harder delivery. Across Kukuu's Chesterfield range, from the armchair through to the four seater, the depth and height stay the same at 94cm and 75cm. Only the width changes as the sofa gets longer, moving from around 106cm on an armchair up to 240cm on a four seater. Because diagonal depth is calculated from depth and height, not width, that means the diagonal depth figure of roughly 120cm stays identical across every size in the range. If a two seater clears your doorway, a four seater in the same collection will clear it too, since width is rarely what stops a sofa getting through a door. What actually becomes the limiting factor on a longer sofa is the length of your hallway and how tight the turn is at the end of it, not the doorway itself.

UK door and access numbers worth having before you order

The hallway turn figure is the one that catches people out most often, because a hallway can be wide enough on its own and still fail at the corner, where the sofa needs that extra diagonal clearance to pivot rather than simply slide straight through.

What to actually measure before you order

Start with the sofa itself, taking depth and height separately rather than relying on a single quoted figure, since the diagonal depth calculation needs both numbers to be accurate. Then measure every doorway on the route from the front door to the final room, not just the room it will end up in, since a lounge door that is wide enough does nothing for you if the hallway door before it is narrower. At any point where the route turns a corner, measure the diagonal across that turn rather than just the corridor width on either side of it, since that diagonal is what the sofa actually has to clear while pivoting.

Where this leaves you

If you are choosing between sizes in the same collection, the width you pick is mostly a room decision rather than a delivery risk, at least for ranges built the way Kukuu's Chesterfield line is, where depth and height hold steady across sizes. You can browse the full Chesterfield sofa collection to compare sizes directly, or look across the wider best leather sofas range if you are still deciding on a style. For the complete current collection of luxury leather sofas UK buyers are choosing from, the Kukuu homepage brings every range together in one place.

Frequently asked questions

What is diagonal depth and why does it matter more than width?
Diagonal depth is the distance from a sofa's bottom front corner to its top back corner once tilted on its side. It matters more than flat width because delivery teams carry sofas through doors on this angle, and it is often considerably smaller than the sofa's listed depth or height on its own.

Will removing a door really make a difference to whether a sofa fits?
Yes, often enough to matter. Taking the door off its hinges and removing the stops typically adds 40mm to 50mm of clear width, which on a tight delivery is frequently the exact margin needed.

Does a bigger sofa in the same range always mean a harder delivery?
Not necessarily. If a collection keeps the same depth and height across its sizes and only changes width, as Kukuu's Chesterfield range does, the diagonal depth stays identical regardless of size, so a larger sofa is not automatically a harder delivery than a smaller one.

What is the standard UK internal door width for sofa delivery?
762mm as a leaf under BS 4787, though the actual clear opening once the frame is fitted usually comes out closer to 686mm to 720mm, which is the figure that matters for a delivery calculation.

What should I measure at a hallway corner, not just the hallway itself?
The diagonal clearance across the turn, not the corridor width either side of it. A hallway can be wide enough along its length and still fail at a 90 degree corner if there is not enough diagonal space to pivot a long sofa through it.