Once you have found a development (or two) that you like, I highly recommend that you take a tape measure with you when you are viewing properties you are seriously interested in. Maybe, not on the first visit to a property, but definitely do on subsequent visits.
Another great tip for 2nd or 3rd visits is to take a paper cut out of your bed size with you … or other large furniture items you have such as a large sofa or corner sofa. Simply use some Sellotape to tape together some bits of newspaper to the exact footprint size of your bed or sofa. Fold or roll them up and bring them to your property viewings of any property that you are very seriously interested in, so that you can see whether your major furniture pieces fit adequately or not. Of course, you could always change your furniture, but there is added cost and hassle in that.
The reason for bringing the tape measure, or cut-outs, is that when you are looking at empty rooms, they will actually appear smaller in your mind than they are. You can fit more into an empty room than you think you can. Using a tape measure or paper cut-outs brings some fact-based measurements into the spatial interpretations.
The developer’s floor plans they will give you the dimensions of a room. Be aware though that not all rooms are straightforward, square or rectangles. There are often little nooks and crannies that you might want to account for also, or a bay window. On the floor plans you might see 4 tiny little triangles in each room. These will be 2 sets of triangles opposite to each other and these are indicators of where the developer’s measurements were taken from.