Perhaps when you were renting or living in a small place, a queen size bed was the right size for you, but now that your room is larger, you want a king. Don't worry, there are ways to retrofit your bed without having to buy a new one. You will, of course, need to buy a new box spring and mattress, but the bed itself can be extended outward. A queen bed is 1.5 by 2m (60 by 80 inches), and a king bed is 1.9 by 2m (76 by 80 inches). Most metal bed frames are adjustable, so simply follow the manufacturer's instructions and adjust the size from queen to king. Adjusting a wooden bed, however, will require more work.
Measure the dimensions of your queen bed. While the mattress is 1.5 by 2m (60 by 80), the bed frame will be slightly larger, to be able to hold the mattress. It should only be about 1.3 to 2.6cm (1/2 inch to 1 inch) larger.
Remove the mattress and box spring from the bed.
Brace the side that you're going to cut with a jack, so that the jack is holding one end of the bed's weight.
Cut the side (not at the head or foot, but a side) off the rest of the frame. The jack should hold the bed upright.
Measure and cut the wood slats, also known as planks, that will be used to make the extensions. This wood should extend 40cm (16 inches) outward from the side, and should contain several extra inches which will be screwed to the underside of the bed. The type of plank, thickness of plank and placement of planks will depend on the current wood's type and layout. Imitate the existing layout on your bed and use the same quality and thickness of wood.
Screw the wooden slats, or planks, to the underside of the bed. Ensure there are at least 7 to 10cm (3 to 4 inches) of support along the underside of the bed, before the plank is exposed and becomes the extension arm.
Brace the planks with C-clamps to the original side that you cut off in Step 4.
Screw or nail the side to the new planks, which now serve as extension arms.
Lower the jack and remove. The bed should now rest on its original legs.
Place a new king-size mattress and box spring on the bed frame.
Always use caution when working with saws, drills or heavy, sharp or blunt objects. Do not allow children or teenagers to undertake this project without strict adult supervision.