The three numbers, and why they travel together
A standard restaurant dining table is 750 mm high. A standard dining chair has a seat height of 450–460 mm. That leaves roughly 290–300 mm between the top of the seat and the underside of the table, which is the space a guest's thighs and knees occupy when they sit down.
Each number looks reasonable on its own. The problem appears when one is changed: a 780 mm table with 460 mm seats gives 320 mm of clearance and the guest sits with their elbows raised; a 460 mm seat under a 730 mm table gives 270 mm and their thighs touch the apron. Neither guest complains about the furniture. They complain that the room is uncomfortable, and the cause is never found.
The practical rule is to write the seat height and the table height on the same drawing and confirm them together. Any factory that quotes a chair without asking what table it sits under is quoting half a product.
Table top thickness quietly eats your clearance
A 750 mm table height is measured to the top surface. The underside sits lower by the top thickness plus the frame. A 25 mm solid timber top on a steel frame may leave the underside at 700 mm; a 40 mm top on a deep timber apron can bring it to 680 mm.
That 20 mm difference is the whole margin between a comfortable knee and a bruised one, and it is invisible in a photograph. When you specify restaurant tables, give the finished height and the top thickness, then ask what the underside height will be. If the answer is not a number, the drawing is not finished.
The same applies to pedestal bases. A cast-iron pedestal with a low profile collar gives more foot room than a square steel plate, and foot room matters more than most buyers expect once the chairs are occupied and guests are sitting at an angle.
Armchairs change the width, not the height
Armchairs are specified at the same seat height as side chairs, so they do not affect the vertical numbers. They change the horizontal ones: an arm adds roughly 80–100 mm of width per side, and an arm that does not fit under the table means the guest cannot pull in.
For a fixed banquette or a wall bench, armchairs only work at the ends. For loose tables, check that the arm clears the apron or the frame by at least 20 mm at the seat height, and that two armchairs facing each other across a two-cover table do not touch arms when both guests are seated.
This is one of the reasons we quote restaurant dining chairs and table and chair sets against the same drawing. A set is not a chair plus a table; it is a checked pair, where the arm and the apron are known to each other before production.
Pull-out space belongs in the specification
Every chair needs 450–500 mm of space behind it for a guest to pull it out and sit down. Measured with the chairs pushed in, a room always looks like it holds more covers than it does, which is why capacity counted from a pushed-in plan is optimistic by roughly one cover in five.
Draw the layout with the chairs pulled out and the aisle measured at the tightest point. If the aisle closes when a guest is seated, service staff will walk the long way round for every plate, and the room will feel smaller than its floor area suggests.
Round tables buy back some of this space because the chair can sit at any angle, which is why 1,200 mm rounds often fit where a 1,200 mm square will not. The trade is that rounds waste more of a rectangular room.
Fixing it on one drawing
The sequence that avoids all of the above is short. Fix the seat height from the intended guest profile and the table height from the service style. Calculate the underside height from the top thickness and frame. Check the arm and the apron against each other. Then draw the room with the chairs pulled out and confirm the aisle.
Only after that is it worth talking about finishes. Custom dimensions on both commercial dining tables and restaurant chairs are quoted at the same price as standard in our workshop, with no tooling fee, so there is no cost reason to accept a stock size that does not fit the room. The cost of changing a dimension after production starts is a new production run.
Two models make the arithmetic concrete. The JP-T123 dining table is a 750 mm top on a pedestal base, where the underside height depends on the top thickness you choose. The JP-S006 table and chair set is a checked pair: the seat height and the underside height are already resolved against each other, so the clearance is fixed before either piece is made.
If you are still at the stage of deciding the room rather than the furniture, the restaurant furniture specification page works through the layout questions in the order they have to be answered. If the numbers are already fixed and you want them checked, send the drawing and we will mark up what does not close — that is part of the quoting work, not a separate service.