Convertible step stool chairs can be found in furniture stores. But if you are an aspiring woodworker, building it yourself is a good way to improve your woodworking skills! You get to practice using various advanced tools in this DIY project.
RL The pin from which I grabbed this chair/ladder combo points to a site that no longer hosts the information. However, I can't help but love the design. Flipped towards the right and it's a chair, flipped opposite, it's a step ladder.