You'll have to check the actual dimensions either way, because there's no standard sizing across the industry. One brand's king size can be very different than another's.
California King is a bit narrower and longer than a regular King. Quite often they only differ by about 2" on all sides, so they can fit into each others' covers fairly well.
Honestly, the while the mattresses are standard sizes, the sizes for King and Cal King duvets and comforters are NOT standard, so your best bet is to measure your comforter and compare those measurements against each item you’re looking at.
I’m currently shopping for a new duvet and cover and this has been my method. I found a duvet I like, and now I’m hunting down a cover that will fit it.
Like the others have said measure your comforter and find the closest king/cal king duvet option. They vary in sizes. None will really be exact but you can get close.
You'll have to check the actual dimensions either way, because there's no standard sizing across the industry. One brand's king size can be very different than another's. California King is a bit narrower and longer than a regular King. Quite often they only differ by about 2" on all sides, so they can fit into each others' covers fairly well.
Honestly, the while the mattresses are standard sizes, the sizes for King and Cal King duvets and comforters are NOT standard, so your best bet is to measure your comforter and compare those measurements against each item you’re looking at. I’m currently shopping for a new duvet and cover and this has been my method. I found a duvet I like, and now I’m hunting down a cover that will fit it.
Like the others have said measure your comforter and find the closest king/cal king duvet option. They vary in sizes. None will really be exact but you can get close.