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The Studio · Calculator

Seat height calculator

Height is a feeling. It can also be measured. Give me the bench, the table and yourself, and I will choose the thickness that puts your feet on the floor and your knees under the table.

Worked out by

The Quiet Geometer of Seattle · · Updated

The quick answer

Subtract the bench height from the sitting height you want, then allow for compression: firm foam sinks roughly 15 % when you sit, softer foam more. A bench already at about 17–18 in usually needs only 2 in (5 cm); leave roughly 10½–12½ in between the seat and a dining tabletop. The calculator picks from standard 2–6 in (5–15 cm) thicknesses and draws you to scale.

The seat height calculator

Every field is live. Change a number and the drawing redraws; copy the link and it opens with your numbers.

Units
The seat
Foam
You

Used to estimate a comfortable sitting height and to draw you.

Around the seat (optional)

A window sill, an air-conditioning unit, a light switch.

Load an example — the ones marked are past projects

Drawing…

Side view to scale. The dashed box is the cushion before you sit; the figure is drawn from your height.
Get a quote with these numbers

Buyer questions

  1. A common question

    Is the foam firm or soft — how much will it compress when I sit? The bench is already at a good height and I don't want to disturb the ergonomics.

    The workshop's answer

    Medium-hard 32-density foam — you won't sink into it. Most buyers choose 3 in; this buyer, with a bench already 17 in high, went for 2 in and added ties to keep it in place.

  2. A common question

    I worry the cushion will be too tall — there's a table next to the bench. Can you make it a touch thinner?

    The workshop's answer

    You choose the thickness when you order: 2, 3, 4 or 5 inches. For a bench next to a table, 2 or 3 inches are the popular choices, for exactly this reason.

  3. A common question

    About how tall is the seat cushion? I'd like my legs to fit under my table.

    The workshop's answer

    It is 6 inches — is that okay for you?

  4. A common question

    My cushions are too high. Can I reorder them thinner?

    The workshop's answer

    Yes — place the same order again and choose the thinner option, for example 2 in instead of 4 in, and say in the note that it replaces a set that sat too high.

  5. A common question

    My bench cushion is too thick to sit on. Can I just put thinner foam in the cover I have?

    The workshop's answer

    The cover was sewn to fit 4 in foam, so 2 in foam inside it would sit loose and baggy. A thinner cushion needs its own cover in the same size and fabric.

A real project

Two boys, a corner bench and two inches

A family in the UK had a corner dining bench, about 71 by 47 in on the outside and 17¾ in deep, with three rounded corners and two small boys who made everything washable by necessity.

The seat was already 17 in high. The workshop suggested 4 in, its usual comfort. The family chose 2 in. At a dining table, 2 in of firm foam kept their knees under the tabletop and their feet flat. Load the dining bench, 17 in example above and you will see why.

They were right. The table decides. The cushion listens.

How to use it

  1. Measure the bench

    From the floor to the top of the seat board. Not to the top of the old cushion.

  2. Decide your sitting height

    Leave it empty and the calculator estimates it from your height. Or sit on a chair you like and measure its seat while you sit.

  3. Add the table

    Floor to tabletop. Between the seat and the tabletop, about 10½–12½ in feels right for eating.

  4. Mind what is above

    A window sill, an air-conditioning unit, a light switch. The cushion's uncompressed top must stay below it.

  5. Check the depth

    Seat depth minus any back cushion should leave a few fingers' gap behind the knee.

  6. Choose, then cut

    A cover is sewn for one thickness. Decide first. Copy the link to keep your numbers.

Olive green outdoor bench cushion on a rustic wooden dining bench at a laid table under festoon lights at duskSave
A long olive pad on a rustic dining bench, laid for dinner under string lights with linen napkins and olive branches.

Questions people ask

How thick should a cushion be on a dining bench?

If the bench is already at chair height (about 17–18 in), 2 in (5 cm) of firm foam is usually enough; 3 in (7.5 cm) if it is a little low. Keep about 10½–12½ in between the seat and the tabletop.

What is a comfortable seat height?

Roughly the height of the back of your knee from the floor with shoes on — about a quarter of your height plus about an inch. Feet flat, thighs level, knees near a right angle.

How much does a foam seat cushion compress when you sit?

Firm high-density foam sinks roughly 15 % under an adult, medium foam about a quarter, soft foam more. That is why a 4 in cushion lifts you by about 3⅜ in, not 4.

Why does my window seat cushion feel too high?

Usually because the seat was built to chair height and a thick cushion went on top. Check the uncompressed top against the sill as well: buyers have kept window cushions at 2 in so they would not cover the window or an air-conditioning unit.

How deep should a seat be?

Deep enough to carry the thighs, short enough to leave a few fingers' gap behind the knee. A deep reading nook is fixed with a back cushion, not a shallower seat.

— Hana

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