It depends on how serious you are about your putting. If you are just looking for a fun weekend activity with friends, then a smaller 8-10ft green should suffice. However, if you are looking to really improve your golf game, then I would recommend a larger green that is at least 12ft wide and 20ft long. This will give you plenty of room to practice your swings and build consistency with each putt.

There is no one perfect size for a backyard putting green, as it can vary depending on your space and needs. However, a good size to aim for is around 12' x 12'. This will give you plenty of room to practice your putts without having to worry about stray balls ending up in your neighbor's yard.