The short answer is that the average height of a standard urban bench seat is about 18 inches from the ground to the top of the seat. In practice, most public benches fall within a 17- to 19-inch range, with 18 inches being the most common target in city parks, transit stops, and plazas.
That height is not chosen by accident. A seat height around 18 inches puts the average adult in a comfortable, stable position: feet flat on the ground, knees bent close to 90 degrees, and hips level or slightly above the knees. This makes it easier to sit down, rest, and stand back up without straining. If you go much lower, the bench can feel like a squat and may be hard for older people or those with knee issues. If you go much higher, shorter users may not be able to plant their feet, which reduces comfort and accessibility.
There is some variation depending on the bench design. Traditional wooden park benches often measure about 17 to 18 inches high. Contemporary metal or concrete benches may come in at 18 to 19 inches. Benches without backs sometimes run slightly lower, while benches with backs and armrests usually stay in the 17- to 19-inch zone. For accessible public seating, many local building codes and design guides recommend this same range, and armrests are often added to help people push up from the seat.
For a DIY or residential bench, you can be a little flexible. A seat height of 16 to 20 inches can work depending on the users and style. But if you want that familiar urban bench feel, set your seat height at 18 inches, or at least keep it between 17 and 19 inches.
So, to answer the question directly: the standard urban bench seat height is typically 18 inches, with a normal range of 17 to 19 inches from the ground to the top of the seating surface.