Why does a mirror seem to flip left and right?

KohakuWhen you raise your right hand in front of a mirror, the person in the mirror seems to raise their left hand. But are left and right really reversed?

The answer in 30 seconds

In fact, what a mirror reverses is not left and right at all.

A mirror does not flip left and right. It only flips the direction straight into the mirror: front and back (depth). The image of your right hand stays on the right side of the mirror, and the image of your head stays on top. Left and right only seem swapped because, in our minds, we picture the person in the mirror as someone else facing us.

Buildings and trees reflected in a roadside mirror — A mirror standing by the road reflects the buildings and trees across from it.Photo: Adrian Tync / CC BY-SA 4.0 / Wikimedia Commons

Mirrors flip front and back

Raise your right hand in front of a mirror, and the image raises the hand on the right side of the mirror too. Your head stays on top and your feet stay at the bottom. So what is reversed? Point your finger at the mirror, and the image's finger points back at you. According to an explanation by a physicist at West Texas A&M University, a mirror only swaps the front and back of an object. It does not swap left and right, or up and down.

Figure: A mirror flips "front and back"

Check it with writing

Hold a sheet of paper with writing on it so that you can see the paper and its reflection at the same time, and compare them. The letters run in the same direction on both. The same explanation says this is proof that a mirror does not swap left and right. The letters only look backward when you turn the paper around to face you, or turn your head to look.

KohakuI recommend reflecting some writing and checking it for yourself.

The left-right swap happens in our heads

We still feel that left and right are reversed because we think of our reflection as "another person standing and facing us." When someone faces you, their right hand is on your left. A physics explanation published on a University of California, Riverside website also says that a mirror only reverses the direction toward the mirror, and that the left-right swap is something we do in our heads.

Lay a mirror down, and up and down flip

If you lay a mirror flat on the floor, what flips is up and down. A lake reflecting the scenery upside down is one example. A mirror always reverses only the direction perpendicular to its surface.

Want to know more?

The backward word "AMBULANCE" on the front of an ambulance is there so that drivers ahead can read it correctly in their rearview mirror without turning around.
Stand a mirror on its side and hold out a sideways arrow pointing at its surface, and the arrow in the image points the opposite way. Placed like this, the mirror does look as if it has flipped left and right.

KohakuA mirror reverses front and back. The feeling that left and right are swapped comes from a switch we make in our own heads.

Quick quiz: test yourself

Which direction does a mirror actually flip?

Show the answer

Left and right
Up and down
Front and back

Front and back A mirror flips only front and back, the direction straight into it. Left and right seem swapped because we picture our image as another person facing us.

Sources

Why do mirrors flip left to right and not up to down?West Texas A&M University (Christopher S. Baird)
Do Mirrors Reverse Left and Right?University of California, Riverside (Physics FAQ)

This article was written after checking the sources above as of 2026-10-03. Explanations may change as research progresses. Photo credits are shown below each photo.