Honestly, if I had to give you one number, I’d say 17 inches is the best outdoor bench height for a seat that both kids and adults will use. Here’s why. Most adult benches are built around 18 inches high, which feels natural for grown-ups. Kids, on the other hand, are usually more comfortable at 12 to 14 inches. A seat height of 16 to 17 inches sits right in the middle—it’s low enough for children to climb onto without struggling, but high enough that adults don’t feel like they are folding themselves down onto the ground.
If adults will use the bench most often, stick closer to 17 inches or even 18 inches. If it’s going in a play area or a family garden with younger children, 16 inches is a better compromise. Seat depth matters too. A depth of 15 to 18 inches gives shorter legs enough room to bend at the knee without cutting off circulation, while still supporting adult thighs. Adding a small footrest, an adjacent stepping stone, or a lower side bench can make the whole setup more comfortable for everyone.
If you want a simple rule: choose a bench seat height between 16 and 17 inches for mixed-age outdoor seating, and look for stable construction with rounded edges.