Matching the nominal 135 × 190 size does not finish the decision. The furniture may be larger than the mattress, open into a wall or produce a finished bed height that does not suit the sleeper.
I would use this size to add storage where 150 cm would damage room circulation. Before paying, confirm external dimensions, inner depth, lid clearance, ventilation, package sizes and the actual delivery and assembly service.
Measure the furniture, not only the mattress
Mark 135 × 190 on the floor, then add the stated thickness of sides, front, headboard and handle. The second outline must coexist with doors, wardrobes, radiators and bedside furniture.
Ask for assembled external width, length and height. A few centimetres can decide whether the room remains easy to clean, walk through and use.
Rehearse the lid movement
The lid needs a clear path and must work with the actual mattress weight. Check wall, headboard, handle position and how far you can comfortably reach into the storage space.
Opening force, grip and controlled closing matter more than a large capacity claim if the divan will be used frequently.
Calculate the finished bed height
Add base, storage body, lid, mattress and protector. The result should allow the sleeper to sit and stand comfortably.
Confirm that the mattress is approved for a flat fixed base and follow its ventilation requirements. A storage divan is not an adjustable bed.
Treat delivery as part of the product
Confirm the number and size of packages and measure every door, lift and turn. Do not assume a piece that fits the bedroom can reach it.
Record whether room delivery, assembly, packaging removal and old-base removal are included, plus the return conditions after opening or assembly.