--- title: "Seat Cushion Height Calculator: Bench, Table & Knees" url: "https://cushionguide.com/studio/seat-height-calculator/" --- *Enter bench height, table height and your own height to find the cushion thickness that keeps feet on the floor and knees under the table, drawn to scale.* 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 [Hana](https://cushionguide.com/masters/hana/) The Quiet Geometer of Seattle · June 24, 2026 · Updated July 9, 2026 ## 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. 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. ## Buyer questions ## 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 Leave a hand's width of floor — and a few fingers behind the knee. 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 Lindqvist The Quiet Geometer of Seattle, Washington Raised in Seattle between her Japanese-American grandmother's tatami room and her Swedish-American father's flat-pack workshop in Ballard. — Hana ## More from the Studio - [Calculator · MaggieBay window calculator](https://cushionguide.com/studio/bay-window-calculator/) - [Calculator · NateTrapezoid cushion calculator](https://cushionguide.com/studio/trapezoid-cushion-calculator/) - [Calculator · ÉlodieFabric yardage calculator](https://cushionguide.com/studio/fabric-yardage-calculator/) - [Calculator · CallumFoam firmness finder](https://cushionguide.com/studio/foam-firmness-finder/) - [3D builder3D bench cushion builder](https://cushionguide.com/studio/bench-cushion-builder/) - [3D builder3D chair cushion builder](https://cushionguide.com/studio/chair-cushion-builder/)