How this calculator works
Mattress sizes are nominal, and the same name can mean different dimensions in different regions: a European double is wider than a North American full, and a European king is narrower than a North American king. The calculator holds a reference table for each region and converts the chosen size to your units. It then adds the walking space you choose on each side of the bed, which is the figure that decides whether the room feels cramped. Length gets the same allowance at the head and the foot, so leave out closets or doors that reduce usable floor.
Formula
room width = mattress width + 2 x side clearance. room length = mattress length + 2 x end clearance. Width and length are taken from the standard table for the chosen region.
Worked example
A queen mattress in North America is 60 by 80 inches, or 152.4 by 203.2 cm. With 60 cm on each side the room needs to be at least 272.4 cm wide and 323.2 cm long. A European king at 180 by 200 cm needs 300 cm by 320 cm with the same allowance.
Advertisement
Frequently asked questions
What is the difference between a full and a double?
In North America they are the same size, 54 by 75 inches. Some retailers use double for a European 140 by 200 cm mattress, which is wider and longer, so check the actual dimensions rather than the name.
How much space should be beside a bed?
About 60 cm allows a person to walk and make the bed. Where two people get up during the night, 75 cm on each side is more comfortable. Storage under the bed reduces the usable width at floor level.
Do these figures include a bed frame?
No. The table gives the mattress only. Frames, headboards and footboards add between a few centimetres and about 20 cm, so measure the frame you plan to use and add it to the length and width.
Why is a California king narrower than a standard king?
It trades width for length: 72 by 84 inches against 76 by 80 inches. It suits tall sleepers in a room where length is easier to find than width.