Size of Bed Bugs

Bed bugs, which are increasingly becoming a problem around the world, are parasitic insects that inhabit sheets, mattresses and furniture. The bugs spend their nights feasting on our blood, causing itching and blemishes. These creatures are extraordinarily small and difficult to spot, but they're far from microscopic.

A jar full of tiny bed bugs.


The size of bed bugs varies greatly, but adults usually top out between 4 and 5 mm in length and 1.5 to 3 mm in width.The size of the bugs depends on how full they are. An engorged bed bug that's just finished a meal measures on the larger end of the scale.

Life Stages

The size of the bed bug increases throughout its life. The larvae are typically around 1.5 mm long and usually grow around 0.5 mm throughout each successive life cycle. Bed bugs undergo four nymphal stages. The bugs molt after each feeding, leading to their next stage of development until they become adults.

Gender Roles

The gender of the bed bug does not affect its size. Males and females reach similar proportions. The females, however, swell when they are ready to mate. This leads to confusion among males, which occasionally attempt to mate with other males that are engorged with blood.

Other Physical Features

Bed bugs are almost always light to dark brown in color, with a hint of red after they've been engorged with blood. They do not use pincers, but instead use two hollow tubes to pierce the skin of their host. They then inject a numbing agent and anticoagulant, and suck out the blood.