Difference Between a California King and a Regular King?

Is a California King and a Regular King the Same Thing?

What many people refer to as a regular or standard king is called an Eastern King by the mattress industry and measures at 76” wide by 80” long. It is the size found in most furniture & mattress stores on display and in stock. The California king also referred to as the western king is 72” wide and 84” long. This is a special size that is normally not stocked by stores. In the past and still today the Cal. King is more commonly used for hard side waterbeds.

Do They Make a Special Mattress to Fit Inside a Waterbed?

Frequently people ask for foam or spring mattresses to drop into a hard side waterbed. The industry name for such a bed is a waterbed insert. This is a mattress undersized 2” in both length and width so you can get your hands between the mattress and frame to make the bed. The finished mattress measures only 70” X 82” a tad smaller than the traditional California King mattress and a great solution for people that own waterbeds.

A common problem when buying a California king mattress and box spring is that there are very few headboards available in the California king size width. When buying a headboard or a headboard and footboard nearly all are only available in Eastern King and then have a second attachment on them for Cal. Kings because of the small 4 inch difference leaving two inches of extra headboard on each side of the Cal. King mattress making it a one King size fits all bed. This is a method that has been used on combination Queen / Full headboards for years. If you place the mattress set on a metal frame make sure it can be adjusted to fit a California king 72 inch mattress width.

In those situations where people decide to transition from their wood frame waterbed but keep their California king insert they will then need to find a box spring to put underneath it. Be aware that if you go out and buy a California king box spring it will be 72” X 84” and your insert may only be 70” X 82”. You may need to order a custom size boxspring to fit your waterbed insert mattress.

Will My Old Sheets Work on My New Bed?

California king and eastern king sheets will not interchange. You may get by with flat sheets, but the fitted sheet definitely will not work. I should point out there are differences between California king sheets for a spring mattress and those made for a waterbed. California kings conventional sheets usually have a flat top sheet and the bottom sheet is fitted like a shower cap making it hard to get on a hard side waterbed. Waterbed sheets on the other hand usually have 4 corner pockets and some top sheets are sewn to the foot of the bottom sheet. We have found separated sheets to be more popular with the top sheet having pockets only on the foot end only and the bottom having a standard pocket in each of the four corners. We call this a 6-pocket sheet set.


Doug Belleville and his father Dave own and run STLBeds - a specialty sleep store located in Arnold, MO. The staff at STLBeds is highly educated about sleep, comfort and their special sleep products. STLBeds only carries high quality mattresses and bed-related products. You won't find the brand names here - just call and ask us why!

9 Comments Leave your comment »

Can a Calif. King bed be altered/adjusted to accommodate a regular King mattress?

Comment by pat — June 2, 2014 @ 11:27 pm

Pat, I am no carpenter :-) however there is some good news, a California King bed with a headboard or a headboard and footboard usually is not a California King size by itself. They often can fit Eastern Kings. You will typically see a second set of hook in slots or bolt up holes to left of the Cal. King slots on the left and to the right of the slots on the right. They can not be altered/adjusted to accommodate because they are designed to fit both sizes. Hope yours has both connection points. Doug

Comment by Douglas Belleville — June 3, 2014 @ 3:37 pm

We are looking for a California King insert for our waterbed frame. I am measuring that the mattress will be 70 x 82. I would like a firm mattress as my husband and I are experiencing some back issues and need to replace our old insert mattress. How many coils should I be looking for to provide the firmness that we need? Will the mattress be at least 10 inches high? Please let me know what you have available, the price, and the shipping information. I am very hesitant to buy a mattress that I can’t try out, but there are no stores I can find one to try in my area.

Comment by Patti — September 7, 2014 @ 6:25 pm

We have an RV which we purchased a waterbed insert mattress in King size. I’m having trouble finding sheets that won’t ride up because of the unusual size. Can anyone tell me where to look for sheets that will fit a waterbed insert mattress? Any help would be appreciated. Thank you

Comment by Kris — September 18, 2014 @ 6:16 pm

Kris, to my knowledge they do not make a specific waterbed insert sheet set. People usually have to to either use their waterbed sheets, over-sized flat sheets. You can also use sheet straps to help with the slipping off or riding up problem. Doug

Comment by Douglas Belleville — September 19, 2014 @ 7:39 am

We have a California king Now, we want to get a just a king, will the box springs still work?

Comment by Mandy — February 17, 2015 @ 4:14 pm

Mandy, No a California king and an Eastern King should not be combined. Doug

Comment by Douglas Belleville — February 18, 2015 @ 7:19 am

Good Morning
Why wont my old Cal Sheets fit my reg (eastern) NEW king bed ?? If it is just the 4 ” the other way , I should be able to put them on just different sides??

Comment by Patty — April 2, 2015 @ 9:00 am

Hi Patty, I must be in a silly mood this morning because this question made me giggle. 72 x 84 is the measurements of Cal. King Your new Eastern King is 76 x 80 The reason they will not fit? We can’t make a round peg fit in a square hole. Please forgive me Doug

Comment by Douglas Belleville — April 7, 2015 @ 11:55 am

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