Honestly, there is not one universal number because a bench’s wobble point depends more on its frame design and hardware than on a single weight rating. That said, a typical well-built outdoor bench made of wood or metal is usually rated for 500 to 800 pounds of evenly distributed static weight. A mid-range plastic or resin bench is often rated for 250 to 500 pounds. Those numbers assume the weight is sitting still and spread across the seat.
Wobble is a different issue from breaking or collapsing. Most benches do not start shaking simply because they are overloaded. They start wobbling because the load shifts sideways, the legs are uneven, the joints are loose, or the ground is soft. In real-world use, a decent bench on a flat patio may feel steady with 400 to 500 pounds of centered weight. By 600 to 800 pounds, you may notice creaking, slight flex, or side-to-side movement, especially if people sit down heavily. A cheap bench with thin metal legs or bolted corner joints can develop a wobble at much lower weights, often around 200 to 300 pounds, particularly when two or three people sit near the ends.
A realistic rule of thumb is this: expect a typical mid-range outdoor bench to remain steady up to about 350 to 450 pounds of active sitting weight on level ground. Beyond that, the weak points are usually not the seat slats. They are the leg connections, bolts, and lack of diagonal bracing. To keep a bench stable longer, tighten the hardware before the season, add rubber feet or pavers under the legs, and choose benches with cross braces or wide leg bases. So the short answer is many outdoor benches can hold 500 to 800 pounds total, but wobble can start much sooner, often in the 200 to 450 pound range, if the frame is lightweight, joints are loose, or the ground is not perfectly even.