A poll done by Petside.com and AP revealed that 50 percent of Americans consider their pet to be just as much a part of the family as any human member. It's no wonder, then, that dog owners will do whatever they can to ensure their doggy is comfortable outside, which is where igloo doghouses come into play. The dome-like structure makes it hard for some owners to determine which size will be best for their dog. However, after a few measurements and considerations, your dog will be sitting comfortably outside.
Measure and weigh your dog or check breed standards to determine what category your dog falls into: small, medium or large. If you are unsure of the category, always round up to rather than down.
Determine the usage your dog will get out of the igloo doghouse. If your dog is mainly an outdoor dog and will use the doghouse as a primary source of shade and shelter from the rain, you may consider the largest igloo doghouse there is. However, if your dog is an indoor/outdoor dog or has 24-hour access to a doggy door, the doghouse will probably be more of a dog toy storage area and can be smaller and less comfortable without it being a big deal.
Think of the primary purpose for the doghouse. If your dog will use the house for much sleep, you may consider putting a dog bed inside of the doghouse, which would take up more room. If you want to put a food dish or water bowl inside of the house, that will also eat up more space. For every item you want to add to the inside, the size of the doghouse needs to increase so that your pet has room to move around and be comfortable.
Visit your local pet store to look closely at different-sized igloo doghouses. Put a dog bed inside one of the larger ones to see how much room is left inside. Bring your tape measure with you and measure the insides of the doghouses. Because of the dome shape, the sides will be shorter than the middle, so you'll want to measure both the sides' height and the middle height for a full perspective.