Why Do I Look Thinner in Some Mirrors and Bigger in Others?
We cut mirror glass for a living, and this is one of the questions we get asked most, usually by someone who has just bought a mirror somewhere else and does not trust it.
The short answer: it is almost never your eyes, and it is almost never a genuinely curved mirror. Here are the four real causes, in the order they actually matter.
First, what a flat mirror really does
A properly flat mirror reflects you at exactly half your height. Stand six feet tall and your reflection occupies three feet of glass, and it stays three feet whether you are standing one foot away or ten. Distance changes how much of the room you see around yourself. It does not change your proportions.
So if you seem to change shape as you walk towards a mirror, that mirror is not flat. Which brings us to why.
1. The glass is too thin and bending
This is the most common cause in a cheap mirror, and it is pure physics. A tall sheet of 3mm glass cannot hold its own weight without bowing slightly. The bow is usually in the middle, which is roughly where your waist sits.
Go to 5mm or 6mm and the panel is stiff enough to stay flat. The taller the mirror, the more this matters, which is why a small 3mm bathroom mirror can be perfectly honest while a five-foot 3mm one is not.
2. It is fixed to a wall that is not flat
Indian walls are rarely perfectly true, and a mirror clipped at four corners onto a wall with a slight belly gets twisted into the shape of that wall. The glass is fine. The fixing is the problem.
Full adhesive onto a flat backing board avoids it. So does mounting on a frame that holds the glass in one plane rather than pressing it against the plaster. If you are hanging a large mirror yourself, hold a straight edge against the wall first.
3. The angle it leans at
This is the big one in a home, and the one nobody thinks about.
A mirror tilted back at the top looks at you from below. Everything nearer the bottom of the glass, meaning your legs and hips, is rendered larger, and you read shorter and wider. Tilt the same mirror forward and the effect reverses: you look taller and narrower.
It is why the leaning mirror in your bedroom and the fixed one in the bathroom disagree about you, even if both are excellent. Neither is lying. They are looking at you from different angles.
If you want the honest version, mount it flat to the wall. If you want the flattering version, lean it forward very slightly at the top. We are not going to pretend nobody does the second one.
4. Deliberate curvature
Genuinely curved mirrors exist and they do exactly what you think.
A convex mirror bulges outward and spreads reflected light apart, so everything looks smaller and further away. That is why they are used as security mirrors and on vehicles, where seeing more matters more than seeing accurately.
A concave mirror curves inward and brings light together, so it magnifies. That is the 3X shaving mirror on your bathroom wall.
Some changing rooms use a very slightly concave mirror to stretch the reflection vertically. The curve required is small enough that the mirror still reads as flat, which is precisely why it works. If you have ever looked noticeably better in a shop than at home, that may not have been the lighting.
And the photographs
Worth separating this out, because it is a different problem. A camera lens is curved. A flat mirror is not.
A phone camera uses a short focal length, which pushes whatever is closest to the lens outwards. In a selfie that is your nose. It is lens geometry, not a verdict on your face, and it is the reason people so often prefer the mirror to the photograph.
How to tell if a mirror is honest
- Walk slowly towards it and watch your outline. If your shape shifts, the glass is bowed.
- Stand to one side and look along the surface at a straight line in the room, a door frame or a tile joint. On flat glass that line stays straight in the reflection.
- Check the thickness. For anything over three feet tall, 5mm or 6mm.
- Check how it is fixed. Corner clips on a bare wall are where the trouble starts.
What we do about it
We cut on 6mm low-iron glass and mount full-length pieces on a flat backing rather than clipping them to the wall, because the flatness is the product. A mirror that changes your shape is not a cheaper mirror, it is a broken one.
Sizes run from 6 inches to 120, made in Delhi, 5-year warranty.