When choosing a length, the most important thing is to focus on your height or the growth of your other half, if it is larger. The minimum height margin should be at least 10 centimeters, but for maximum comfort, preferably more.
As for the width of the bed, it is enough to lie down on it and, throwing your hands behind your head, spread your elbows. If you have enough space in your half, then the bed is right for you. If not, consider other options.
Regarding the shape, we can say that the most rational choice will be in favor of a standard rectangle. But if you pursue an exquisite originality and want a round, oval, arched or even heart-shaped bed, then you are doomed to encounter indispensable difficulties. Not only will it take up more space, but also bed linen will have to be sewn to order. Do not forget about the selection of blankets and rugs.
There are two main types of frames: with two supporting backs and two side panels, or with four side panels and backs, where the legs or podium protrude. It is believed that the frames with legs are less durable, but if the assembly is carried out efficiently, it does not matter which option you choose, it will last you a long time.
Often the base consists of a frame on which flexible lamellas are placed. Moreover, the more lamellas, the stronger the base. In a standard single bed there should be at least 15. There are also options with springs and metal grills, but it is believed that they are inferior to models with lamellas in orthopedic properties.
When considering the base, it is worth paying attention to what will be under it. You can choose the classic version, where there is nothing under it, then the mattress will be well ventilated, and this is important. But if you want to save space, then a lifting base with hidden compartments or a base with drawers will be a great option.