[financial] How much do I charge for custom paintings?

I’m an independent artist and I’m trying to establish some pricing guidelines—I’m pretty new and have a hard time asking for a lot of money. I do a lot of 8x10 hand painted house portraits with acrylic and they are detailed but I’m just not sure what to charge. Also, I have no idea how long they take bc I always forget to time myself. I want to add a pic but idk how lol