What size bathroom mirror do you need?
Mirror sizing has one published rule and a lot of opinion. Here is the rule, the published sizes, and the depth figure people forget.
By Sawyer V. · · How we research
The short answer
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Quick picks
Tap any row for the full write-up. Prices are checked against Amazon rather than remembered — where we have no verified figure the button says so.
| # | Product | Best for | Renter | Price |
|---|---|---|---|---|
| 1 |  Verdera 20 x 40 in. Medicine Cabinet 20 in. wide by 40 in. tall, 3-7/8 in. deep, with four adjustable shelves behind the mirror. | A 24 in. vanity, with storage | Ask first | |
| 2 | No photo yet Vitality Wall Mirror, 24 x 30 in., Edge Lit, with Defogger 24 x 30 in., edge lit, with a defogger — the size most single vanities are built around. | A 30 in. vanity | Owner-only | |
| 3 | No photo yet Vitality Wall Mirror, 24 x 40 in., Glow, with Defogger 24 x 40 in. of mirror with front and side diffusion and a published CRI of 90+. | A tall wall over a single vanity | Owner-only |
The one published rule
Nearly everything written about mirror sizing is convention. One thing is not. The ADA Standards state: “Mirrors located above lavatories or countertops shall be installed with the bottom edge of the reflecting surface 40 inches (1015 mm) maximum above the finish floor or ground. Mirrors not located above lavatories or countertops shall be installed with the bottom edge of the reflecting surface 35 inches (890 mm) maximum above the finish floor or ground.”
Those are accessibility requirements for regulated spaces rather than a law for your own bathroom, but they are the only published heights in the category, and they are a sound default: a mirror whose bottom edge sits above 40 in. starts excluding people.
Width: stay inside the vanity
The published sizes cluster at 20, 24 and 30 in. wide because vanities do. The convention worth keeping is simple — the mirror should not be wider than the vanity below it, because the moment it is, it starts competing with the light fixture and the wall for the same space.
- 24 in. vanity: a 20 in. mirror or cabinet.
- 30 in. vanity: a 24 in. mirror, leaving a few inches either side.
- 36 in. and up, or a double vanity: either one wide mirror or two, one per basin.
Height: what the glass is for
A mirror has to cover the range of heights that will use it. Published mirror heights in our catalog run 30, 33 and 40 in., and the taller ones exist to serve households where people differ by a foot. If you are choosing between 30 and 40 in. of glass on the same wall, the taller one is the more useful object, provided the bottom edge still sits at or below 40 in. from the floor.
Depth: the measurement people skip
A flat mirror projects a fraction of an inch. A medicine cabinet does not: Kohler publishes a 3-7/8 in. body plus a 15/16 in. door on the Verdera, which is nearly 5 in. into the room. In a bathroom where two people pass behind each other, that is the difference between a mirror and an obstacle. Mirror against cabinet is compared here.
If the mirror lights itself
A lighted mirror changes the sizing question, because the mirror is also the fixture. Robern publishes CRI 90+ and a footnote worth reading on the lumen figure — “Mirror measured not the raw LED. Based on 48" x 36" Mirror” — so the brightness quoted is not measured on the size you are buying. The LED mirrors are ranked here.
If you rent
Hardwired and recessed mirrors rate Owner-only. A tenant who wants a bigger or better-lit mirror is looking at a freestanding or battery-powered option instead. Renter-friendly mirror upgrades are covered here.
Every pick in full
3 we would buy. Each carries its Renter-Safe Install Rating, the published specs behind it, and the honest gap in what we know.
1. For a narrow vanity
Verdera 20 x 40 in. Medicine Cabinet
Kohler · K-28030 · best for a 24 in. vanity, with storage
20 in. wide by 40 in. tall, 3-7/8 in. deep, with four adjustable shelves behind the mirror.
Kohler’s Verdera cabinet publishes 20 in. wide by 40 in. tall, with a 3-7/8 in. body depth plus a 15/16 in. door, and “Four adjustable tempered-glass shelves”.
A tall, narrow mirror is the right answer over a narrow vanity, and the cabinet version buys storage for the depth it costs you. Recessed against surface-mount is compared here.
Renter-Safe Install Rating
- Drilling
- Required
- Tools
- Not published
- Time to fit
- Not published
- Power
- None
- Reversible on move-out
- With patching when surface-mounted; no when recessed
Why: Surface-mounted, it is screw holes a landlord may agree to. Recessed, it means cutting into the wall between the studs, which is an owner's job.
Read from published documentation, not from fitting one. Kohler — Verdera 20 x 40 in. medicine cabinet K-28030 specification sheet. How the verdict is derived: renter-safe ratings explained.
What’s wrong with it
Nearly 5 in. of total depth projects into a small room, where a flat mirror projects almost none.
What we can’t tell you
Kohler does not publish a weight for the cabinet on its product page.
Published specifications
| Size | 20 in. wide x 40 in. tall; 3-7/8 in. body depth plus a 15/16 in. door on Kohler's drawing |
|---|---|
| Mirrors | “Front mirror, inside door mirror, and back panel mirror”; a “Vertically adjustable 3x magnifying mirror” inside the door |
| Shelves | “Four adjustable tempered-glass shelves” |
| Door | “Slow-close door prevents slamming”; left- or right-hand swing |
| Material | “Anodized aluminum construction with a durable rustproof and chip-resistant finish” |
| Mounting | “Surface-mount or recessed”; hardware included for surface installation |
| Required accessory | K-28033 40 in. mirrored side kit |
| Faucet clearance | The door must clear the faucet by at least 3 in. (76 mm) |
| Warranty | “KOHLER® One-Year Limited Warranty” |
Source: Kohler — Verdera 20 x 40 in. medicine cabinet K-28030 specification sheet
#ad Price $694.01 as of October 18, 2026. Prices change; Amazon’s listing is the one that counts. How we’re funded.
2. The standard size
Vitality Wall Mirror, 24 x 30 in., Edge Lit, with Defogger
Robern · YM2430RSFPD3 · best for a 30 in. vanity
24 x 30 in., edge lit, with a defogger — the size most single vanities are built around.
Robern’s Vitality 24 x 30 in. is the middle of the range, with “Mirror defogging” and a 2 in. wide lighted edge on Robern’s own front-view drawing.
24 in. wide under a 30 in. vanity leaves 3 in. of counter either side, which is the proportion most bathrooms are designed around.
Renter-Safe Install Rating
- Drilling
- Required
- Tools
- Not published
- Time to fit
- Not published
- Power
- Standard outlet behind the mirror
- Reversible on move-out
- With patching
Why: Surface-mounted to the wall, with the outlet behind the glass. A fixing and an outlet, both the property's.
Read from published documentation, not from fitting one. Robern — Vitality Wall Mirror YM2430RSFPD3 specification sheet. How the verdict is derived: renter-safe ratings explained.
What’s wrong with it
It is hardwired and rates Owner-only, so it is a remodel purchase rather than a weekend one.
What we can’t tell you
Robern footnotes its lumen figure as measured on a larger mirror than this one.
Published specifications
| Defogger | “Mirror defogging”; model number key “D = Defogger Included” |
|---|---|
| Light pattern | “S = Edge Lit”, with a “Front and side diffuser, no visible LED's” |
| Lighted area | 2 in. (51 mm) wide on Robern's front-view drawing |
| Dimming | “Dimmable LED task lighting to 1%”; “Compatible with most Triac/Phase-cut dimmers” |
| Color temperature | 2700K on this sheet — Robern's 24 x 40 in. sheet lists 3000K and notes the change from 2700K, so the two sheets disagree |
| Color rendering | CRI “90+”, R9 value “50+” |
| Light output | “Lumens* (Estimated)” of “1120”, footnoted “Mirror measured not the raw LED. Based on 30" x 40" Mirror” |
| Power | “Watt Output - LED with optional defogger on”: “85w max” |
| Electrical | “120 Vac 60Hz wall outlet as shown in drawing”; plug-in |
| Dimensions | Height 30 in. (762 mm), width 24 in. (610 mm), depth 1-3/4 in. (45 mm) |
| Mounting | “Constructed for surface mounting”; hardware and security bracket included |
| Listings | UL 962; CSA-C22.2, No. 250.4 |
| Warranty | Not published on the specification sheet |
Source: Robern — Vitality Wall Mirror YM2430RSFPD3 specification sheet
#ad We have no verified live price for this one right now, so we are not showing a number. How we’re funded.
3. When the ceiling allows
Vitality Wall Mirror, 24 x 40 in., Glow, with Defogger
Robern · YM2440RGFPD3 · best for a tall wall over a single vanity
24 x 40 in. of mirror with front and side diffusion and a published CRI of 90+.
The 24 x 40 in. Vitality adds 10 in. of height over the 24 x 30. Robern publishes “Front and side diffuser, no visible LED’s”, CRI “90+” and an R9 value of “50+”.
Height is where mirrors go wrong: taller looks generous in a showroom and can put the top of the glass above where anyone actually looks.
Renter-Safe Install Rating
- Drilling
- Required
- Tools
- Not published
- Time to fit
- Not published
- Power
- Standard outlet — Robern's drawing puts the outlet behind the mirror
- Reversible on move-out
- With patching
Why: It is surface-mounted to the wall with a security bracket and plugs into an outlet Robern's drawing places behind the glass. Both the fixing and the outlet belong to the property.
Read from published documentation, not from fitting one. Robern — Vitality Wall Mirror YM2440RGFPD3 specification sheet. How the verdict is derived: renter-safe ratings explained.
What it costs to run — Electricity
- Power
- 85 W maximum, with the defogger on (Robern's published figure)
- Use
- 2 hours a day (our example)
- Rate
- 18.34 cents per kWh (US residential average, June 2026)
85 W x 2 h x 365 / 1000 x $0.1834 = $11.38
About $11 a year at two hours a day, with the defogger running
Arithmetic on published specifications, not a measurement. Rate source: U.S. Energy Information Administration, Electric Power Monthly Table 5.6.A — US residential average 18.34 cents/kWh, June 2026.
What’s wrong with it
At 40 in. tall it needs the wall height, and the ADA's 40 in. rule fixes where its bottom edge starts.
What we can’t tell you
Robern's published lumen figure is footnoted as measured on a 48 x 36 in. mirror, not this size.
Published specifications
| Defogger | “Mirror defogging”; the model number key reads “D = Defogger Included” |
|---|---|
| Light pattern | “G = Glow”, with a “Front and side diffuser, no visible LED's” |
| Dimming | “Dimmable LED task lighting to 1%”; “Compatible with most Triac/Phase-cut dimmers” |
| Color temperature | 3000K on this sheet, which notes Vitality mirrors moved “to 3000K CCT from 2700K CCT” in Fall 2021 |
| Color rendering | CRI “90+”, R9 value “50+” |
| Light output | “Lumens* (Estimated)” of “2170”, with Robern's own footnote: “Mirror measured not the raw LED. Based on 48" x 36" Mirror” — so the figure is not measured on this size |
| Power | “Watt Output - LED with optional defogger on”: “85w max” |
| Electrical | “120 Vac 60Hz wall outlet as shown in drawing”; “Plug-in mirror, saves on install time” |
| Dimensions | Height 40 in. (1016 mm), width 24 in. (610 mm), depth 1-3/4 in. (45 mm) |
| Mounting | “Constructed for surface mounting”; “All hardware with security bracket included” |
| Construction | “Anodized aluminum back frame”; “Quality polished edge mirror” |
| Listings | UL 962; CSA-C22.2, No. 250.4 |
| Warranty | Not published on the specification sheet |
Source: Robern — Vitality Wall Mirror YM2440RGFPD3 specification sheet
#ad We have no verified live price for this one right now, so we are not showing a number. How we’re funded.
Where to buy
Everything recommended on this page, in one place. Each link is an Amazon Associates link — we earn a commission at no extra cost to you, and it never decides a pick.
- $694.01View on Amazon
Verdera 20 x 40 in. Medicine Cabinet
Kohler · K-28030 · Renter verdict: Ask first
- Check price on Amazon
Vitality Wall Mirror, 24 x 30 in., Edge Lit, with Defogger
Robern · YM2430RSFPD3 · Renter verdict: Owner-only
- Check price on Amazon
Vitality Wall Mirror, 24 x 40 in., Glow, with Defogger
Robern · YM2440RGFPD3 · Renter verdict: Owner-only
#ad Prices are not shown because we only publish figures we have verified on the day. How we’re funded.
Questions people actually ask
how big should a bathroom mirror be
No wider than the vanity below it. Published sizes cluster at 20, 24 and 30 in. wide: a 20 in. mirror suits a 24 in. vanity, and a 24 in. mirror suits a 30 in. vanity.
how high should you hang a bathroom mirror
The ADA Standards put the bottom edge of the reflecting surface at 40 inches maximum above the finish floor over a lavatory, and 35 inches maximum where there is no lavatory below. Those are the only published heights in the category.
how deep is a medicine cabinet compared with a mirror
Much deeper. Kohler publishes a 3-7/8 in. body depth plus a 15/16 in. door for its Verdera cabinet, close to 5 in. into the room, against a fraction of an inch for a flat mirror.
should a mirror be the same width as the vanity
It should not be wider. Matching the vanity width works when the wall has no sconces; where side lights are fitted, a narrower mirror leaves them room.
Sources
Read next
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