Can vary from 6mm-9mm.
Bed Bugs are small brownish insects. They are relatively flat. They are almost as wide as they are long. They are an oval shape with horizontal lines running along its body. Nymphs or immature bed bugs resemble adults but are much smaller and are sometimes clear.
Bed Bugs are parasites that prefer to feed on human blood. Bed Bugs are nocturnal and feed manly at night. This is why they prefer beds. But they will infest couches, chairs, any furniture etc. They are capable of producing a painless bite allowing them to feed on their host without being noticed. The bites will later become irritated and have rash like symptoms becoming red and itchy.
Call a professional for an inspection. Remove all clutter to make the inspection easier. Be careful when moving clutter not to transfer the bugs. Personal item such as cloths, stuffed toys, and blankets should be put in the dryer for 30 minutes at least. The heat from the dryer will ensure the bed bugs that went into the dryer are dead. Then the items should be placed in a plastic bag for a few days. Empty and dismantle all furniture to the furthest extent possible. Then apply the appropriate insecticide around all infested and possible infestation areas. If you believe to have an infestation the best thing to do is contact a professional.