King vs California King Duvet: What Fits Which Bed

A standard king mattress is 76 by 80 inches and a California king is 72 by 84, so the Cal King is 4 inches narrower and 4 inches longer. A duvet cut for a standard king will usually hang short at the foot of a Cal King, and a duvet cut for a Cal King leaves less overhang on the sides of a standard king.

The way around that is a single oversized duvet, cut wide and long enough to drape over both, which is how most people end up solving it once they measure.

The two mattresses, side by side

Before comparing duvets, get the beds straight. Both are king beds, both sleep two people comfortably, and both are about the same total area. The shape is what differs.

The California king is the taller person's bed. If someone in the house is over 6 feet 2, that extra 4 inches at the foot keeps their heels on the mattress. The standard king gives each sleeper 38 inches of width, which is the same as a twin bed each.

Why duvet sizes are so inconsistent

Unlike mattresses, duvets have no enforced standard sizes in the US. One brand's king duvet is 102 by 86 inches, another's is 104 by 90, and a third calls 108 by 96 a king. Some brands sell a separate Cal King duvet and some do not.

That is why the label on the bag tells you less than the dimensions printed under it. Always look at the actual inches.

Here is what a duvet has to cover on each bed if you want it to hang at least 12 inches down the sides and reach the foot without pulling off the pillows:

Notice the pattern. The king needs more width, the Cal King needs more length. A duvet that satisfies both numbers, at least 100 inches wide and at least 94 inches long, fits both beds.

The mattress thickness problem

Those minimums assume a mattress around 10 inches thick. Modern mattresses are often 12 to 16 inches, and a pillow top or a mattress topper adds more. Every extra inch of mattress height eats an inch of drape on each side.

A 14 inch mattress with a 102 inch wide duvet on a standard king leaves 13 inches of drape per side, minus 4 extra inches of height, which is 9 inches, barely enough to hide the top of the fitted sheet. Go wider and the problem disappears.

The same math applies at the foot. If you tuck the duvet under the mattress at the bottom, add another 8 to 10 inches of length. If you let it hang, add whatever drape you want to see.

The size up trick

Interior designers and hotel housekeepers do the same thing: they put a bigger duvet on the bed than the size label suggests. A king duvet on a queen, or an oversized king on a standard king, gives the full drape you see in photos, where the duvet falls past the box spring and the bed looks upholstered.

For a standard king or Cal King, that means picking a duvet around 106 inches wide and 98 inches long. On a standard king that is 15 inches of drape per side and 18 inches of extra length for the fold at the head or a tuck at the foot. On a Cal King it is 17 inches per side and 14 inches of extra length.

Both look intentional. Neither looks like a duvet that is slightly too small, which is the look most people are trying to escape.

The one caution: an oversized duvet on a bed pushed against a wall will bunch up on the wall side. Pull the bed out a few inches or fold the wall side under.

Matching the cover to the insert

The other place king sizing goes wrong is the cover. If your insert is 106 by 98 inches and your cover is a standard 104 by 90 king cover, the insert will not fit. If the cover is bigger than the insert, the insert slides around inside it and the corners empty out.

Buy the cover and the insert together, from the same maker, in the same measured size. Then check that the insert has corner loops and the cover has corner ties, and tie them. Four small knots keep a big duvet from migrating toward one sleeper.

Quick answers

• Can I use a king duvet on a California king? Yes, if it is at least 94 inches long. Many standard king duvets are 86 to 90 inches and will look short.
• Can I use a Cal King duvet on a standard king? Yes, if it is at least 100 inches wide. Narrow Cal King duvets will show the sheet along the sides.
• Do I need two different duvets for two different king beds? No. One duvet around 106 by 98 inches covers both with drape to spare.
• What about a full or queen? A queen duvet around 87 by 87 inches covers a 60 by 80 queen or a 54 by 75 full with drape on all sides.

This is why the PureFlow Duvet Heaven Set comes in one King / Cal King size, cut at 106 by 98 inches (270 by 250 cm) to drape over either mattress, with the matching cotton cover cut to the same dimensions and corner loops on the insert so nothing shifts. The Queen at 87 by 87 inches fits queen and full beds the same way.