Instruction: Generate an answer to the question by utilizing the information contained in the document.

Input:
Question: What is the diameter of the bottom of the kettle?
Document: The kettle is beautiful and (usually) whistles loudly and nicely. But after a few days of use, some brown spots formed on the inside bottom. Rust maybe? I cleaned it over and over with baking powder and vinegar, and lemon juice, but the spots aren't really gone. I thought that with stainless steel, that wouldn't happen.
Like most All-Clad items, this is nicely made, although done in China. The kettle is larger than I would have thought, although a thorough reading of the description would have made that easily known. It works well on the induction stove, but would have been much more efficient with a more substantial metal bottom. Would have preferred a brushed finish, the shiny finish will be impossible to keep clean and free of finger prints.
It took me a long time to select a new tea kettle. I'm a little picky, and very choosey. The All-Clad tea kettle is just the ticket! I make tea for ice tea in it easily, due to the wide opening, making it easy to drop large qt. size tea bags down into hot water. This tea kettle is handsome sitting on my stove, and with a wide bottom, fits over  a burner, thus heating water quickly.
Have always had an All Clad kettle. This replaced my old one. Despite being made in China, it still has the reliable thick body construction included in all All Clad products. Its a huge pot and the thick bottom is great for my gas range. I'm not a fan of the whistle so I just keep the spout lid open at all times. The whistle is not loud though. I wish there was a plastic component on the handle to eliminate a pot holder (handle gets hot!)
It just makes sense.Lastly, I don't know much about other brands of oven, but we have a Wolf, and the burners are so large that the flames would fly up the sides of my copper Chantal kettle and burn the patina. The All Clad has the same diameter as our Wolf burners, so no chance of that happening; although I suspect if it did, no harm would come to it.So thank you, Steve, for burning out my Chantal kettle!
I love the way the lid gently slides on, instead of having to be rammed in, as with the other two brands. What is more, because the base is of a wider diameter, water heats in half the time.I honestly don't know why other reviewers complain so about the handle heating up. Have you tried the Chantal? You virtually need to wear an asbestos suit before you can touch its handle.
This tea kettle was a gift for my wife who has been wanting it for awhile. It has met all her expectations.
I would not recommend some one who likes Tea Kettle with whistle like me.
I am very happy with my new kettle. It is worth every cent I paid for it.
Yes the product is OK. But not whistling. I believe I bought a Whistling Kettle which is part of reason for the purchase.
Answer: It appears to be about 10 inches. It covers the gas burner grill plate on my stove. Great kettle and doesn't show burn marks.