How to Measure Up for Bookcases: A Simple Sizing Guide

To measure up for a bookcase, you need four numbers: the width of the wall or alcove at its narrowest point, the height to the ceiling or any obstruction such as a picture rail, the depth you can spare without blocking a walkway, and the clear width of every door and staircase the bookcase must pass through on its way in. Measure each one twice, at more than one point, and allow a small margin so the unit can be manoeuvred into place.

That is the short answer. The detail is where most sizing mistakes happen, especially in older UK homes where walls lean, skirting boards protrude and alcoves are rarely the same width top to bottom. Our range of modern bookcases UK sale lists full dimensions for every design, and this guide explains how to match those numbers to your room.

What You Will Need

• A metal tape measure, ideally at least five metres long.
• A pencil and notepad, or your phone for notes and photographs.
• A spirit level, useful for checking floors and walls.
• Masking tape, for marking an outline on the wall or floor.
• A second person, which makes measuring tall spaces far easier and safer.

Work in centimetres throughout. Most furniture dimensions in the UK are listed in centimetres or millimetres, and mixing units is a common source of error.

Step One: Measure the Width

Measure the width of the space at three heights: just above the skirting board, at waist height and at the top. In a straight wall this tells you how much room you have. In an alcove, it reveals whether the walls are parallel. In many period homes, chimney breasts and alcove walls are slightly out of true, and the narrowest of the three readings is the one that counts.

Remember the skirting. If the bookcase will sit flush against the back wall, the skirting board will push it forward unless the base is designed to clear it. Note the skirting depth and height so you can check whether a unit will sit tight to the wall or need a small gap.

Allow clearance at each side. A centimetre or two either side of an alcove makes it far easier to slide the bookcase in. A unit that is exactly the width of an alcove on paper rarely fits in practice.

Width also affects how the bookcase relates to everything else on that wall. If a sofa, sideboard or TV unit sits nearby, note their positions too, so the bookcase can be planned as part of the room rather than in isolation. Our modern living room furniture UK range is a useful reference for how pieces of different widths sit together.

Step Two: Measure the Height

Measure from the floor to the ceiling at the point where the bookcase will stand. Then note anything that interrupts that height: a picture rail, coving, a sloping ceiling, a light switch, a radiator or a window sill.

Tall bookcases are usually delivered upright or assembled in place. If yours arrives fully built, you need enough height to tilt it from horizontal to vertical. A useful rule is that the diagonal of the bookcase, measured from a bottom corner to the opposite top corner, needs to be less than the ceiling height. Otherwise it may catch on the ceiling as you lift it.

Ceiling heights vary widely across the UK housing stock, from lofty Victorian rooms to lower modern builds, so never assume a standard figure. Measure your own room, and measure it at both ends if the floor or ceiling looks uneven.

Step Three: Measure the Depth

Depth is where comfort and practicality meet. Most paperback and standard hardback books fit on shelves around 25 to 30cm deep. Larger art books, atlases and box files may need 35cm or more.

Before choosing a depth, look at how much floor space you can give up. Stand where the front of the bookcase would be and check that doors open freely, that you can walk past comfortably and that sofas or chairs are not crowded. Marking the footprint on the floor with masking tape is a simple way to see the effect before you commit.

In hallways and landings, keep depth to a minimum. A shallow unit holding paperbacks is usually more practical than a deep one that narrows the route through the house.

Step Four: Measure the Route In

This is the step people forget. A bookcase that fits the room is no use if it cannot get there. Measure the width and height of:

• The front door and any internal doors on the route.
• Hallways, especially at turns.
• Staircases, including the headroom above the stairs and the width at any half landing.
• Lifts, if you live in a flat.

Compare these with the bookcase dimensions, remembering that a tall unit may need to be tilted to get round a corner. If a fully assembled unit will not pass, a flat packed design built in the room may be the answer.

Step Five: Check the Floor and Walls

Use a spirit level on the floor where the bookcase will stand. Old floorboards often slope, and even a small gradient can make a tall unit lean forward. Many bookcases have adjustable feet, or you can use furniture shims to level the base.

Check what the wall is made of. Tall bookcases should always be fixed to the wall to prevent tipping, and the fixing you need depends on whether the wall is solid brick, plasterboard on studs or something else. Locate any pipes or cables before drilling.

Planning Shelf Spacing

Once you know the outer dimensions, consider what you will store inside. Shelf spacing affects how many books a unit holds and how it looks.

• Paperbacks generally need around 20 to 25cm between shelves.
• Standard hardbacks sit comfortably in around 28 to 32cm.
• Large format books and magazines often need 35cm or more.

Adjustable shelves give the most flexibility. If the shelves are fixed, check the internal heights against the books you own, and measure your tallest volumes rather than guessing.

Proportion and Visual Balance

Measurements tell you what fits. Proportion tells you what looks right. A few guidelines help:

• In an alcove, a bookcase that fills most of the width and height looks built in and considered.
• On an open wall, leave space either side so the unit does not look squeezed.
• Pair two matching bookcases either side of a fireplace or window for symmetry.
• In a low ceilinged room, a wider, lower bookcase can feel more comfortable than a tall, narrow one.

Bookcases are one part of a living space, so consider how the unit sits with your sofa, coffee table and media storage. Step back to the doorway and look at the taped outline from there, since that is how most people will first see it.

When a Bookcase Is Not the Right Answer

Sometimes the measurements point to a different piece. If you have very little depth, open shelving with slim uprights may work better. If you want to mix books with display pieces, a shelving unit with varied compartments can be more flexible. Our shelving units and storage UK sale range includes ladder, cube and open frame styles for these situations.

If you want to protect collectables or fragile books from dust, a glazed cabinet is worth considering. Our modern display cabinets UK come in a range of heights and widths to suit alcoves and open walls. Cabinets follow similar sizing principles to bookcases, and our article on display cabinet dimensions and shelf spacing in UK homes goes into more detail on heights, depths and shelf gaps.

Room height matters just as much as width. If you live in an older property or a converted space, our guide to UK ceiling heights by property age is useful background before you choose a tall unit.

Write It All Down

Before you start comparing designs, gather everything into a short note:

• Maximum width, at the narrowest point.
• Maximum height, below any obstruction.
• Comfortable depth.
• Skirting depth and height.
• Narrowest door, hallway and stair width on the route.
• Wall type for fixing.

Keep a photograph of the space alongside the numbers. When you are ready, you can compare designs against your measurements at Furniture in Fashion, with free delivery to most UK mainland postcodes.

Frequently Asked Questions

How much gap should I leave around a bookcase in an alcove?

Around one to two centimetres either side is usually enough to slide the unit in without damaging the walls. Leave a little more if the alcove walls are noticeably uneven.

What is a standard bookcase depth?

Many bookcases are roughly 25 to 35cm deep. Shallower units suit paperbacks and narrow spaces, while deeper ones hold large format books and files.

Do I need to fix a bookcase to the wall?

Yes, any tall bookcase should be secured to the wall to prevent it tipping forward. Use fixings suited to your wall type and check for pipes and cables first.

How do I know a tall bookcase will stand up in my room?

Measure the diagonal of the bookcase from a bottom corner to the opposite top corner. If that measurement is less than your ceiling height, you should be able to lift it upright.