How can I reupholster RV cushions?

Use the existing cushion covers as a pattern. Purchase durable, yet washable fabric and sew away! Hope that is what you are looking for.

Naomie has the right idea, take the current cushion covers off and that will be your pattern. Joann's fabric store has a good selection of appropriate materials for your new cushion covers. Or you could also look to Amazon for fabrics.

Here is a video on how to make a box cushion.... https://www.youtube.com/watch?v=zhcEe3z0kig

Can the cushions be removed from the backings or bases in the RV?

If so, then follow instructions for recovering any box-style cushion.

If not, then special upholstery tools may be required to complete the job.

You could recover them with easy envelope cushion or pillow covers. This is how I make easy easy pillow or cushion covers: https://momhomeguide.com/easy-envelope-pillow-covers-for-spring/

If you’d like to make a piped box cushion, here’s how I made a simple one for a window seat: https://momhomeguide.com/diy-window-seat-box-cushion/

Oops in my lengthy reply I left my email address and after hit send. I remembered I think everyone sees our comments and replies. I was being totally genuine. Oops. If you do email me please be specific and let me know it’s you. I hope I don’t get spammed to death now. Yikes, I was just excited.