Unless your veterinarian advises otherwise, the correct height for your dog's food bowl is right on the floor. Dogs are designed to eat at ground level, and doing otherwise puts them at risk for gastric dilatation and volvulus syndrome, aka GDV. This is a potentially life-threatening condition involving a dilated, pressurized stomach that's at risk of twisting or rupturing. However, in certain circumstances the benefits outweigh the risks of using elevated dog feeders. In these cases, it's important for your dog's comfort and safety to determine the correct bowl height. Involve your vet.
Ask your veterinarian about using an elevated dog bowl if your dog has the neurological disorder megaesophagus that interferes with proper swallowing. Also, inquire about using one if your dog has arthritis, a neck injury, a back or spinal problem, or another condition that makes lowering her head to floor level uncomfortable or painful.
Bring your dog into a room with a level, hard floor, not a carpeted surface. Bring a tape measure with you.
Kneel down next to one of your dog's front legs. Make sure she's standing straight up with her feet right below her.
Feel for your dog's withers, which are the apexes of her shoulders, on the leg in front of you.
Determine the distance from the floor to her withers using your tape measure.
Reduce the measurement by 7 inches. This is approximately the correct height for her food bowl in an elevated feeder, which should come to the bottom of her chest region.