Custom

How to design a custom sofa: size, depth, arms, cushions and covering

By the Blankspace design teamUpdated October 21, 20264 min read

The short answer

To design a custom sofa, start with the room: decide the width (leave 30 to 36 in walkways), then choose seat depth by how you sit (21 to 24 in upright, 25 in or more for lounging), seat height around 17 to 19 in, an arm style that fits the space, a cushion fill for the feel you want, and a covering that suits how the sofa will be used. Confirm it fits through every doorway before ordering.

Remember

Width comes from the room: keep 30 to 36 in walkways and 14 to 18 in to the coffee table.
Seat depth sets the feel: 21 to 24 in for upright sitting, 25 in or more for lounging.
Slim or track arms save several inches of seat width over rolled arms.
Foam keeps its shape; foam wrapped in fibre or down feels softer but needs plumping.
Performance fabric or protected leather suits children and pets.

Contents

1. Width: start from the room

Mark the sofa on the floor with tape before you choose a number. Leave 30 to 36 in for walkways, about 14 to 18 in between the sofa and the coffee table, and a few inches from walls and radiators. Allow roughly 24 to 30 in of seat per person, then add the arms.

2. Seat depth and height: how you sit

If you…	Seat depth	Seat height
Sit upright, read, have shorter legs	21 to 23 in	17 to 18 in
Mix sitting and lounging	23 to 25 in	17 to 19 in
Lounge, are tall, or put feet up	25 to 28 in+	18 to 19 in

Deep seats look generous but leave shorter people perched on the edge; you can always soften a firmer, shallower seat with cushions, but not the other way round.

A sofa in profile: seat height is measured from the floor to the top of the seat cushion, seat depth from the front edge to the back cushion.

3. Arms and back

Track arms (straight, squared) are clean and save width.
Slope or slim arms keep a sofa light in small rooms.
Rolled arms are traditional and comfortable but take several inches of seat.
Armless modules suit sectionals and open plans.

Tight backs look tailored and need no plumping; loose back cushions are softer and easier to replace.

4. Cushion fill

Fill	Feel	Care
High-resilience foam	Supportive, holds shape	Low
Foam wrapped in fibre	Softer edge, still supportive	Occasional plumping
Foam with down/feather wrap	Sink-in, relaxed look	Regular plumping
Pocketed coils under foam	Springy, durable support	Low

Quiete by Blankspace — Shown: Quiete, Blankspace Italia, from $7,840.

5. Covering

Choose by use, then colour. Performance fabrics and protected (pigmented) leathers suit families and pets; linen, velvet and bouclé suit lighter use. See leather vs fabric and the upholstery fabric guide for durability numbers.

6. Check it fits, then order

Measure every doorway, stair turn and elevator on the delivery route against the sofa's height, depth and diagonal depth. Then build it in the Blankspace sofa configurator, or have an advisor check the plan with you through the interior design service.

Questions people ask

What is a good seat depth for a custom sofa?

For upright sitting, 21 to 23 inches suits most people; 25 inches or more suits lounging and taller people. If two people of very different heights share the sofa, a medium 23 to 24 inch depth with a loose back cushion is a good compromise.

What sofa width should I choose?

Choose the width from the room: leave 30 to 36 inches for walkways and roughly 24 to 30 inches of seat per person, plus the arms. A three-seat sofa is typically 72 to 90 inches wide; tape the outline on the floor before ordering.

What is the most durable sofa cushion filling?

High-resilience foam, especially over pocketed coils, is the most durable and keeps its shape with little care. Down or feather wraps feel softer but need regular plumping.

Can you make a sofa to exact measurements?

Many custom makers offer set width increments or module counts; fully exact dimensions are usually bespoke. Check which dimensions a model allows you to change before you plan the room around it.