How to Fix A Loose Bicycle Chain

Determine if your chain is loose. As shown in the pictures, the bike chain is hanging low; this is an excellent indication that your bike chain is loose.

Use a bike stand or wall to help keep your bike from falling.

Loosen both nuts on either side of the rear wheel using a socket wrench, rotating the wrench from left to right.

Hold the end of the bike wheel with one hand and the bike's frame with your other hand.

Pull the wheel back from the frame.

Hold the wheel in place while proceeding to the next step.

Tighten both of the loose nuts using a socket wrench, rotating the wrench from right to left, while still holding the wheel back.

Check if your chain is still loose. As shown in the pictures, your chain should have more tension making it straight rather than hanging.