How can I change an armless chair to one with arms?

Hello! I think this link might be able to help you! https://www.hunker.com/13403583/how-to-build-arms-on-a-chair

For it to look natural, I would take it to a furniture repair shop and see what they can do. Sometimes they need to be curved, carved, etc. Maybe too much for a DIY project.

Structure of dining room chairs is exposed and that’s to your benefit.

keep in mind that the arms should not extend all the way to the from of the seat pan, unless you’re ok with them getting banged up.

also keep in mind the top of the arm must not hit the bottom of the table apron. Or they can’t be pushed under the table.

Buying a new computer chair is an expensive solution. There is another option. I once repaired an old handle. We unscrew the finished handle with a screwdriver. This is what the handle looks like from the back side. We measure the length and width including the folds. I got 57 cm by 14 cm. We take a piece of leather. In this case an old leather coat. I think you can use thick fabric or denim. Cut the strip. Cut out the strip. Insert our handle. Secure the ends with thread. Apply glue and wrap the seam allowances, holding them in slightly. The handle is ready; you can screw it into place. I used glue that I had at home. It says on it that it is suitable for leather. I found all this information at https://ballachy.com/best-turkey-choke-for-remington-870-super-mag/ . There is a lot of useful information there.