The short answer is 18 inches. If you measure from the ground to the top of the bench seat, 18 inches is the standard height that feels comfortable for most adults. A range of 17 to 19 inches is also totally normal, and that little window gives you room to adapt for different users or cushion thickness.
Why 18 inches works comes down to body mechanics. For most people, this height lets feet rest flat on the ground, keeps knees close to a 90-degree angle, and avoids pressure under the thighs. If a bench is much lower than 17 inches, taller people often feel like they’re squatting or using their knees too much to stand up. If it’s much higher than 19 inches, shorter people may find their feet dangling, which makes seating less stable and less comfortable.
If you’re buying or building an outdoor bench, use 18 inches as your default. For a built-in bench with a cushion, account for the cushion height. A 2-inch cushion will add about 2 inches of seating height, so you might want the frame closer to 16 to 17 inches. For a hard-top bench with no cushion, stick closer to 18 inches.
Seat depth also matters. A depth of 15 to 18 inches tends to work well for most adults. Less than 15 inches can feel shallow, while more than 18 inches can make shorter people feel like they can’t sit back without their legs sticking straight out. If you’re adding a backrest, a slight backward tilt of about 5 to 10 degrees makes the bench feel noticeably more comfortable.
For public spaces, accessibility guidelines often point to a seat height of 17 to 19 inches, which is why you’ll see that range on many commercial park benches. For a residential patio bench or garden bench, 18 inches is the safe, comfortable standard. If the bench will be used by kids, older adults, or people of very different heights, you can pair it with footrests, cushions, or a lower secondary seat to make the space more flexible.
So if you only remember one number, make it 18 inches. It’s the standard outdoor bench height for good reason: it fits the widest range of bodies, keeps seating stable, and feels comfortable for everyday use.