Seat Depth Advisor
Get a sofa seat-depth range that suits your height — an upright depth for support and a deeper lounge depth — with guidance on back cushions.
Recommended seat depth
Around average height — a mid-range depth suits you; use the back cushions to fine-tune between upright and lounging.
Upright depth lets you sit back with your lower back supported and feet flat; lounge depth is for stretching out. A back cushion or bolster reduces effective depth if a sofa runs deep.
Why depth decides comfort
Of all a sofa’s measurements, seat depth is the one people most often get wrong and most often regret. Get it right and you sink back with your spine supported and your feet on the floor; get it wrong and you either perch on the front edge or slide down until the front rail catches behind your knees.
Because comfortable depth follows the length of your thigh, it scales with height — so this advisor gives a range rather than a single number, from an upright depth for everyday sitting to a deeper one for lounging. When a sofa runs deeper than suits you, a back cushion or bolster brings the backrest forward and closes the gap.
Frequently Asked Questions
What is a good seat depth for a sofa?
Most sofa seats fall between about 50 and 65 cm of usable depth (front rail to the face of the back cushion). The right figure depends on your height: this tool gives an upright depth, where you can sit back with your lower back supported and feet flat, and a deeper lounge depth for stretching out. Taller people are comfortable with a deeper seat; shorter people usually want a shallower one.
How does my height change the seat depth I want?
Seat depth tracks the length of your thigh, which scales with stature. A seat that is right for someone 190 cm tall will leave someone 155 cm tall perched on the edge or unable to reach the backrest. That is why the recommended range shifts deeper as height increases, and why a sofa shared by very different heights is a compromise best solved with cushions.
What if a sofa I love is too deep for me?
Add a firm back cushion or a lumbar bolster. It moves the effective backrest forward and reduces the usable depth, letting a shorter sitter sit back with support and feet on the floor. Deep 'lounge' sofas are designed to be used this way, which is why they often ship with extra scatter cushions.
Does seat depth affect back support?
Yes. If the seat is too deep for you, your back never reaches the backrest and you lose lumbar support; too shallow and the seat edge presses behind your knees. Matching depth to your height — and topping up with a back cushion where needed — is the simplest way to get supportive, comfortable seating.
Is this a medical or ergonomic assessment?
No. These are general comfort estimates from height alone and don't account for posture, mobility, back conditions, or seat height and cushion firmness. Sit-test a sofa where you can, and seek professional advice for a specific medical or postural need.
Estimates for planning — not professional interior-design, ergonomic, or medical advice. Sit-test where you can and measure your own space and doorways before you buy.