A comfortable sofa: seat depth, seat height and foam
A comfortable sofa isn’t simply a soft one. Comfort comes from seat height, seat depth, back height and the foam inside, and each has a number you can measure.
Common seat measurements, drawn to scale. The bar below is 20 cm.
The numbers at a glance
Seat height
Measured from the floor to the top of the cushion. Most sofas sit at 43 to 48 cm,[1] and most people are comfortable between 43 and 51 cm.[2] Your own measurement is the distance from the floor to the back of your knee: seated, your hips and knees sit at roughly a right angle with your feet flat.[4]
A low seat is harder to get out of; below 46 cm with a depth over 58 cm, standing up takes effort.[3] That is why a slightly higher seat suits older people and anyone with sore knees.[4]
Seat depth
Measured from the front of the cushion to the inside of the back. Standard depth is 51 to 56 cm, comfortable for sitting upright; depth for lounging or tucking your feet up is 58 to 66 cm.[2] If you sit all the way back and your feet leave the floor, the seat is too deep for you.
| Who sits | Seat height | Seat depth |
|---|---|---|
| Most people | 43–51 cm | 51–56 cm |
| Shorter (under about 165 cm) | 43–47 cm | 48–53 cm |
| Taller (over about 183 cm) | 47–51 cm | 56–61 cm or more |
| Standing up is hard (knees or hips) | 47–51 cm, with a firmer cushion | Under 58 cm |
Figures from Keck Furniture and Houzz, converted from inches.[2][3]
Back height
From the floor to the top of the back, usually 81 to 102 cm.[2] Backs lower than 71 cm often feel less comfortable.[1] If you want the back to support your head, measure from the seat to the top of your ears: that is the least height the back needs above the seat.[4]
Foam: density is not firmness
Density is how much the foam weighs for its volume; firmness is how it feels under your hand. The two are independent.[5] Higher-density foam generally lasts longer and keeps its shape, so the fabric stays taut.[5] Firmness is measured as the force needed to press the foam down by a quarter of its thickness.[6]
FoamOrder, a foam fabricator, says a seat for daily use needs about 40 to 46 kg/m³, that about 29 kg/m³ is the practical minimum for seating, and estimates that foam of about 29 kg/m³ lasts only about 2 to 4 years.[7] These are the company’s own figures, not a standard, but they tell you what to ask. In any shop, ask for the seat foam’s density as a number.
Try it in the showroom
Sit all the way back: feet flat, knees near a right angle, no gap under your thighs and no pressure at the front edge. Feel for support at your lower back. Stand up and sit down a few times, and try the way you actually sit at home.[2] Small differences in back angle and arms change comfort a lot, so try more than one piece.[4]
Pieces in this article
Questions we hear often
What seat height is comfortable?
Most sofas sit at 43 to 48 cm. Your own measurement is the distance from the floor to the back of your knee.
What seat depth should I choose?
51 to 56 cm for sitting upright, and 58 to 66 cm if you like to lounge or tuck your feet up.
Which sofa suits older people?
A slightly higher seat, about 47 to 51 cm, with a firmer cushion and a depth that isn’t too deep, so standing up is easier.
Does foam density or firmness matter more?
They are different things: density relates to how long the foam lasts, firmness to how it feels. Ask for both as numbers.
Want a hand choosing?
Send us the room and door measurements, or a photo of the space, on WhatsApp and we’ll help you choose. If you’d rather sit on the piece first, both showrooms are open every day.
New Cairo Showroom
Street 26, New Cairo
Sat – Thu: 12:00 PM – 11:00 PM · Fri: 1:30 PM – 11:00 PM
Directions on the map ↗Nasr City Showroom
113 Mostafa El-Nahaas St., Nasr City
Sat – Thu: 12:00 PM – 11:00 PM · Fri: 1:30 PM – 11:00 PM
Directions on the map ↗Sources
The numbers in this article come from these references. They are common sizes, not fixed measurements. Each NOAH piece’s own measurements are on its page.
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Understanding Sofa Dimensions: the First Step on Your Sofa-Buying JourneyArticle · Livingetc · 25 September 2024. Used for: most sofas having a seat height of 17–19 in (43–48 cm), and backs lower than 28 in (71 cm) often feeling less comfortable.
Open the source on livingetc.com ↗ -
Sofa Comfort Guide: Seat Height, Seat Depth, and Cushion FillsGuide · Keck Furniture · 6 January 2026. Used for: standard depth 20–22 in (51–56 cm) and lounge depth 23–26 in (58–66 cm), back height 32–40 in (81–102 cm), sizes for shorter and taller people and for sore knees, and the showroom sit test.
Open the source on keckfurniture.com ↗ -
Sofa Secrets: How to Choose the Right Seat Depth and CushionsArticle · Houzz · 31 December 2016. Used for: a seat lower than 18 in (46 cm) can be hard to get up from, especially when the depth is over 23 in (58 cm).
Open the source on houzz.com ↗ -
Choosing a chair and chair accessoriesFactsheet · Living Made Easy (Disabled Living Foundation). Used for: the right seat height being the distance from the floor to the back of the knee, a higher seat making it easier to stand, and back height measured from the seat to the top of the ears.
Open the source on livingmadeeasy.org.uk ↗ -
IN•TOUCH Vol. 1 No. 2: The Importance of DensityTechnical bulletin · Polyurethane Foam Association · revised 2016. Used for: density being separate from firmness, and higher density generally lasting longer and keeping its shape.
Open the source on pfa.org ↗ -
IN•TOUCH Vol. 1 No. 1: Flexible Polyurethane Foam: a PrimerTechnical bulletin · Polyurethane Foam Association · revised 2016. Used for: firmness (IFD) being the force needed to press foam down by 25% of its thickness.
Open the source on pfa.org ↗ -
FoamOrder Learning Center: couch cushion foamGuide · FoamOrder (foam fabricator). Used for: seat foam of 2.5–2.9 lb/ft³ (about 40–46 kg/m³) for daily use, 1.8 (about 29) as the practical minimum, and the expected life of each density. These are the company’s own figures.
Open the source on foamorder.com ↗
Every NOAH piece carries a 5-year warranty + lifetime maintenance.