How to measure for a sectional before you buy

A sectional is the single most returned piece of furniture in a home, and the reason is almost never taste. It is that it physically would not go in. Half an hour with a tape measure before you shop removes most of that risk, and all of it is arithmetic you can do on a phone.

Step 1 — measure the wall run, honestly

Measure each wall the sectional will sit against, at about ankle height where the sofa base actually lands, not at chest height where the tape is easier to hold. Then subtract, in order:

• Skirting boards and any trim that stops the frame sitting flush — typically 15–25 mm (under an inch) on each end.
• Radiators, vents and thermostats you cannot block.
• Door swings. Take the door’s width and swing an arc; that arc is unusable floor.
• Walkway. Leave at least 750 mm (30 in) for a main route through a room, and 450 mm (18 in) between the sofa front and a coffee table.

What is left is your true wall run. A sectional that matches it to the inch will look and feel wedged; aim to leave 100–150 mm (4–6 in) of air at each open end.

Step 2 — work out which orientation you need

Sectionals are sold as left-facing or right-facing, and the convention trips up almost everyone. Sit on the sofa facing out into the room. If the long chaise is on your left, it is a left-arm-facing (LAF) chaise. If it is on your right, right-arm-facing (RAF).

Some retailers describe it from the standing-in-front view instead, which reverses the answer. If a listing does not say which convention it uses, ask, or judge from the photographs rather than the label. On a one-of-one piece there is no swapping it later.

Step 3 — measure the route in

Walk the exact path the sofa will travel, from the kerb to the room, and measure the tightest point of each of these:

• Every doorway, at the frame, not the opening — and remember you can usually take the door off its hinges for another 40 mm or so.
• Hallway width, and hallway width at a turn, which is the real constraint.
• Stair width, and the headroom above the landing where the piece has to pivot.
• Lift car depth, width and door height, if there is one.
• Any low soffit, light fitting or ceiling fan on the path.

The diagonal depth rule

A sofa does not go through a door standing upright; it goes through tipped on its back or its end. What has to clear the opening is the diagonal from the highest back point to the lowest front point.

Take the sofa’s height and depth, square each, add them, and take the square root. A sofa 900 mm high and 950 mm deep has a diagonal of about 1,310 mm (roughly 52 in). If your tightest doorway height plus door width cannot accommodate that on the tilt, the piece is not going in whole — regardless of how the room measures.

This is the number that catches people, because listings publish width, depth and height and almost never publish the diagonal.

Step 4 — check whether it comes apart

Most modular sectionals separate into two to five pieces, which makes the route problem far easier: you are then measuring for the largest single module, not the assembled whole. Some do not separate at all. Some separate but have a fixed chaise that is itself the biggest piece.

Ask specifically: how many pieces does it break into, what is the largest one, and does it need tools. On our listings the answer is on the item page under Details where the piece has been checked, and if it is not there, ask us before you drive out.

Step 5 — tape the footprint on the floor

The last step is the one that changes minds. Mark the sectional’s outline on your floor with painter’s tape at full size, then live with it for a day. Walk the route to the kitchen. Open the door onto it. Sit a chair where the chaise will end.

People routinely discover at this point that the piece they wanted swallows the room, or that a smaller apartment sectional would leave the walkway they actually use. Tape costs three dollars and it is the cheapest furniture decision you will make.

A worked example

Living room wall: 4,200 mm. Skirting takes 40 mm. A doorway at one end swings 800 mm into the run. Leaving 120 mm of air at the open end gives a true maximum of about 3,240 mm — so a 3,400 mm sectional that “fits a 4.2 m wall” does not fit this one.

Front door is 810 mm wide, 2,030 mm high. The sectional’s largest module is 1,700 mm wide, 900 mm high, 950 mm deep — diagonal about 1,310 mm. Tipped on its end, the 810 mm door width against the 950 mm depth is the binding constraint. Off the hinges, the door gives about 850 mm. Tight, and worth confirming the module depth to the millimetre before committing.

Before you drive out

Every piece on our floor is a single unit, so a wasted trip costs you the trip and costs us the piece sitting there. Bring the four numbers, and if a dimension you need is not on the item page, ask before you set off — we will go and measure the actual piece rather than quote a manufacturer’s spec sheet.

See the sectionals currently on the floor, or read what to bring when you come to collect.

Common questions