Great question. The typical park bench seat height is 17 to 19 inches from the ground to the top of the seat surface, and many manufacturers aim for about 18 inches. For elderly folks, I would treat 18 inches as the sweet spot. At that height, most older adults can sit down and stand up without excessive knee bending, and their feet can stay flat on the floor for stability.
If the seat is lower than about 16 inches, it forces a deeper knee bend and makes standing up much harder, especially for people with arthritis or weak hips. If it is higher than 20 inches, shorter seniors may feel unstable because their heels lift or their feet dangle. So if you are choosing a bench for a senior-friendly space, stay between 17 and 19 inches, and check the actual bench because armrests and cushions can change the effective seat height.
Beyond height, look at seat depth. A depth around 18 to 20 inches tends to work well for older adults, because they can sit back against the backrest without the front edge digging into the knees. Very deep benches of 22 inches or more can make it hard for a shorter person to use the backrest. A supportive backrest with a slight recline of about 5 to 10 degrees is also helpful.
Armrests are one of the most important safety features. Aim for armrests that are 7 to 9 inches above the seat surface and extend slightly forward, because seniors use them to push off when standing. A bench without armrests is much less comfortable and less safe for older users.
If the bench is in a public area, choose a model that meets ADA bench height guidelines, which call for a seat height of 17 to 19 inches. That range is also a good baseline for residential gardens and senior living courtyards.
Material matters too. Smooth wood or recycled plastic with rounded edges is comfortable and low-maintenance. Avoid dark metal benches in full sun if possible, because they can become hot. Place the bench on firm, level ground and leave enough space beside it for a walker or cane.
Quick checklist: seat height 17–19 inches, target 18; seat depth 18–20 inches; armrests 7–9 inches above seat; backrest with slight recline; level non-slip surface.