L.T.
I think the answer to that depends on how well he handles the stairs, does he hold on to something for support, is he a child who is still clumsy and falls a lot. My kids wanted to walk up stairs without holding my hands probably between 2-2 1/2 years. I let them but followed closely behind so if they fell I could stop them from rolling all the way down. My son was about 3 1/2 and my daughter was about 3 when I started letting them navigate stairs without me following behind.