If you want a straight answer: a 6-foot urban bench comfortably fits three adults, and a 4-foot park bench comfortably fits two. That is based on the standard outdoor seating guideline of about 24 inches of hip room per person.
A 6-foot bench is 72 inches long. Divide that by 24 inches, and you get three comfortable seats. In a city setting, that number often stays at three because many urban benches have armrests or divided seat panels that define individual spots. You might squeeze four smaller adults or kids onto the same bench, but elbows will touch, bags will crowd legs, and nobody really feels relaxed.
A 4-foot park bench is 48 inches long. Using the same 24-inch rule, it seats two adults comfortably. Park benches usually have a more open design without center armrests, so three people can sit there in a pinch, especially if one is a child or everyone knows each other well. But for everyday comfort, two is the honest number.
The real answer also depends on body size, clothing, bags, and bench design. In winter coats, a 6-foot bench can feel tight with three people, while a backless bench may allow more sideways movement. Armrests reduce the usable length, and a bench with a center divider can turn a 6-foot urban bench into three marked seats. Without armrests, people tend to spread out, so a 4-foot park bench might realistically hold two adults plus a small child or a backpack.
So if you are planning seating for a public space, office patio, or park, use these practical numbers: plan for three adults on a 6-foot urban bench and two adults on a 4-foot park bench. If you need extra capacity, add more benches or choose longer lengths rather than assuming people will happily squeeze together.