There should be a standard depending upon what shape your toilet is. You have two choices. Look online first, for the shape you need. The other option is to go to the store with the old seat OR find that toilet in store and read what size you need. There may be booklets to look up by model, similar to car headlights and windshield wipers. Lastly, ask the Home Depot experts. They have always helped me get what I need.
Many toilet seats are pretty universal. You can find universal ones too. But to be sure just know what toilet you have when you go.
You can stop in to your local Home Depot, with the model info for your unit and they should be able to assist you.
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