How Big Are Bed Bugs? (See Them on Weird Things)

Published on
December 12th, 2021 
Updated on February 17th, 2024

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Are you afraid of bed bugs — you know, those scary little critters that sometimes find their way into your bed (or your sleeping bag) in the dead of night?

But have you ever seen one up close? It’s certainly no sight for the faint of heart!

So let’s do it. Yep, that’s right… let’s get up and close and see them for what they are!

Bed Bug Quick Facts

1. A bed bug can survive for upwards of an entire year without a meal!

2. Bed bug eggs are small — generally between 0.08 and 1 millimeter in length, which is just under half the size of a grain of salt.

3. Fully grown adult bed bugs can reach lengths up to 5-6 millimeters (3/16 – 1/4 inch) with an approximate width of 3-4 millimeters (3/32 – 1/8 inch). They’re oval in shape and have a reddish-brown color.

4. Newly hatched bed bugs (nymphs) can be difficult to see with the naked eye but will grow to adult size within a few weeks if they’re able to feed on blood.

5. Bed bugs are small, parasitic insects that feed on human blood, typically while their hosts sleep. Despite their unsettling presence and the itchy, uncomfortable bites they leave behind, there is currently no scientific evidence to suggest that bed bugs transmit diseases to humans. The concern with bed bug bites mainly revolves around allergic reactions, potential skin infections from scratching, and the psychological stress associated with dealing with an infestation.

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It’s important to note that while bed bugs have been studied for potential roles in disease transmission, researchers have not found them to be carriers of infectious agents that are harmful to humans. This sets them apart from other blood-feeding insects, such as mosquitoes and ticks, which are known vectors for diseases like malaria, Lyme disease, and several viral illnesses.

How Big are Newly Hatched Bed Bugs (Nymphs)?

Bed bug nymphs are smaller than adults, growing from 1.3 to 4-5 millimeters in length.

They have translucent bodies, but as they grow, nymphs molt and shed their skin many times over the course of multiple weeks.

Can a Bed Bug Change Its Size?

In short, yes. The average adult is about a quarter (1/4) of an inch long, but their flat bodies look significantly bigger after they’ve had a blood meal.

Once engorged with food, the pest will increase in length (and width) for upwards of 12 hours before returning to its normal size. This happens after it finished digesting its previous meal which can last from two days to several weeks!