A mirror is one of the cheapest items in a bathroom renovation — and one of the easiest to get wrong in a way every guest notices. Too small looks bolted on; too large crowds the tapware and throws the whole wall off balance. Get it right, and the mirror does the quiet work of making the room feel considered and complete.
This guide covers exactly how to size a bathroom mirror: by vanity width, shape and installation height, for every common layout from a 600mm powder room vanity to an 1800mm double vanity — matched to real InVogue mirrors and cabinets so you can go straight from measurement to purchase.
12 min read · Last reviewed 22 July 2026 · Reviewed by the InVogue Design Team
Why Trust InVogue?
InVogue Mirrors & Bathware is an Australian-designed mirror and bathware brand trusted in over 10,000 New Zealand homes, specialising in LED smart mirrors and mirror cabinets. The sizing principles below come from that same experience — matching real mirrors to real vanities, not just what looks good in a catalogue photo.
The 30-Second Sizing Rules
- For rectangle, arch and oval mirrors, aim for a width around 70–90% of your vanity width.
- Round mirrors are the exception — a circle carries less visual width than a rectangle, so they usually look best closer to full vanity width.
- Centre the mirror over the vanity, not the wall, and leave roughly 100mm between the top of the tapware and the bottom of the mirror.
- If you're unsure between two sizes, the slightly larger option almost always looks more considered. Double vanities can suit one oversized mirror or two individually sized mirrors — see the Double Vanity Guide below.
Bathroom Mirror Size Calculator
Measure your vanity's benchtop width, find the matching row below, and you have a shortlist in under 30 seconds.
| Vanity Width | Mirror Width | Best Shapes | Start Here |
|---|---|---|---|
| 600mm — powder room | 500–600mm | Round, Arch | The Amalfi 600mm; Positano Cabinet for storage |
| 750mm — ensuite | 650–760mm | Round, Organic | The Lucca 760x890mm; Milan Cabinet 750x700mm |
| 900mm — family bathroom | 750–900mm | Rectangle, Round | The Florence 900x700mm |
| 1200mm — premium ensuite | 1000–1200mm | Rectangle, Arch | The Santander 1200x800mm |
| 1500mm — large family bathroom | 1300–1450mm | Rectangle, Arch | The Santander 1500x1000mm |
| 1800mm / double vanity | 1600–1750mm as one piece, or two mirrors at 800–850mm each | Rectangle (single), or two matching mirrors | The Florence 1800x1000mm, or two 900x700mm units — see the Double Vanity Guide below |
These six widths cover almost every New Zealand vanity. If yours falls in between — say 1050mm — round to the nearest size and size down slightly rather than overhang the benchtop.
Which Mirror Type Do You Need? A Simple Decision Tree
If you'd rather work it out step by step than scan a table, start here.
Do you have a single vanity?
↓ Yes — Is it under 900mm wide?
↓ Yes — Do you need extra storage?
↓ Yes → Mirror Cabinet (try the Positano or Amalfi Cabinet)
↓ No → Smart Mirror (try the Amalfi or Positano)
↓ No (900mm or wider) — Do you need extra storage?
↓ Yes → Mirror Cabinet (try the Milan Cabinet)
↓ No → Smart Mirror (try the Florence, Venice or Santander)
↓ No (it's a double vanity) — see the Double Vanity Guide below.
For the full reasoning behind mirror cabinets vs. smart mirrors, see our companion guide, Mirror Cabinet or Bathroom Mirror?
What Our Designers Recommend Most Often
900mm vanities: a rectangle — it's the width where our full Florence and Venice range opens up. 1200mm vanities: arch, if the room already has a curved detail, since the Santander is sized specifically for this width.
Powder rooms: round, almost every time — there's rarely storage to worry about, and a circle softens a small room. Family bathrooms: storage wins the argument more often than shape — we'd rather start with a cabinet size that fits and pick the finish second.
How Mirror Shape Changes Sizing
The 70–90% rule is a starting point, not a fixed law — the right size shifts depending on the mirror's shape. (For a deeper look, see our companion guide, Round vs Arch vs Rectangle Mirrors.)
Round Mirrors
Because a circle loses visual width toward its edges, a round mirror sized using the rectangle rule often looks smaller than intended — a 600mm round mirror over a 600mm vanity reads as balanced, not oversized. On a high ceiling, pair one with a pendant or wall light above to fill the vertical space it doesn't gain on its own. Round mirrors suit powder rooms, ensuites, and contemporary or Mediterranean-style bathrooms particularly well.
Recommended products: The Amalfi (600mm to 1200mm), Amalfi Cabinet (800mm, with storage) — proportions stay balanced from a compact 600mm powder room to a spacious 1200mm ensuite.
Arch Mirrors
An arch mirror's straight sides keep the 70–90% rule in play — what changes is the height, since the curve draws the eye upward and makes the wall feel taller than the frame suggests. Arch suits ensuites, powder rooms, and any vanity with a curved detail elsewhere in the room.
Recommended products: The Positano (600x900mm, narrower vanities), The Santander (1200x800mm to 1500x1000mm, wider vanities or a statement piece).
Rectangle Mirrors
A horizontal rectangle suits standard-height ceilings and wide vanities; a vertical orientation works well over a narrow single-basin vanity or beside a shower screen, drawing the eye upward on higher ceilings. It's the most flexible shape for family bathrooms, double vanities, and a clean, architectural look.
Recommended products: The Florence and The Venice (900x700mm to 1800x1000mm), Milan Cabinet (750x700mm to 1500x700mm) — the Florence and Venice work particularly well at 900mm, matching a standard single vanity.
Organic & Irregular Mirrors
An organic mirror carries more visual weight than its measurements suggest, so it can often be sized slightly narrower than the standard rule and still read as the room's focal point — best as a single statement piece against a simple, straight-lined benchtop.
Recommended products: The Lucca (760x890mm, 940x1090mm), Lucca Cabinet (760x870mm, with storage) — suits a 750mm vanity especially well, since 760mm sits just at the benchtop edge without overhanging.
Mirror Height Guide
Width gets most of the attention, but height matters just as much for how a mirror functions day to day. (We cover this in more depth in How High Should You Hang a Bathroom Mirror?)
- Eye level: centre the mirror at eye level for the main user — roughly 150–165cm from the floor to the centre of the mirror. In a mixed-height household, centre to the tallest regular user; a rectangle mirror gives more height for the same footprint, which usually suits a shared family bathroom better. Children can still see themselves via the lower portion, so a family mirror rarely needs lowering specifically for kids.
- Clearance above the tapware: leave around 100mm between the top of the tap (or the basin, if there's no tap in the way) and the bottom edge of the mirror — the same rule applies whether the tapware is wall-mounted or bench-mounted.
- Spacing below the ceiling: for a tall rectangle or arch mirror, leave at least 100–150mm between the top of the mirror and the ceiling or cornice.
- Basin type: a vessel basin sits on top of the benchtop, effectively raising the rim, so mount the mirror correspondingly higher to keep the same clearance. An undermount basin sits below the benchtop, so the benchtop and tapware remain the reference points and standard clearance applies.
Double Vanity Guide
A double vanity gives you a genuine choice: one large mirror, or two individually sized mirrors. One oversized mirror creates a calm focal point and suits a contemporary style, at the cost of less definition between the two basins. Two mirrors give each person their own space and reinforce symmetry, but only if they're identical in size and shape and each centred over its own basin — a mismatched pair reads as an error, not a design choice. Leave enough gap between two mirrors for a wall light without crowding either one; a single large mirror's integrated LED lighting usually removes the need for a separate light altogether.
Recommended products: one Florence, Venice or Santander sized to the full vanity width; or two matching units of The Amalfi or The Positano, one centred over each basin. The Florence suits a full-width approach because its clean line reads as one continuous statement, while two Amalfi rounds work well as a pair since their matching diameters keep the wall balanced.
Small Bathroom Sizing Guide
In a small bathroom, mirror size does more work than anywhere else. A mirror close to the full width of the vanity reflects more of the room and light — the simplest way to make a small space feel bigger — so position it to reflect a window or light fitting rather than a blank wall. A mirror cabinet is worth considering too, since it reclaims storage without extra floor space, and a frameless edge reads as less bulky than a framed mirror of the same size.
Recommended products: The Amalfi (round, 600–800mm), Positano Cabinet (500x900mm arch, with storage). Neither needs a benchtop wider than 600mm to look proportioned.
Common Mirror Sizing Mistakes
- Too small: leaves empty wall space either side of the vanity and reads as an afterthought.
- Too large: overhangs the vanity or crowds the tapware, unbalancing the wall.
- Hung too high or too low: breaks the visual connection to the vanity, and can clip shorter or taller users' reflections.
- Wrong proportions for the shape: sizing a round mirror using the rectangle rule (or vice versa) leaves it looking mis-sized for its actual footprint.
- Poor spacing on a double vanity: mirrors not centred over their own basin, or two different sizes, break the symmetry the layout depends on.
- Wrong shape for the room: a heavily curved mirror in a linear, minimalist bathroom — or a hard rectangle in a room full of soft curves — fights the room instead of complementing it.
- Ignoring lighting: choosing a mirror with no integrated lighting in a bathroom with no other light source near the vanity. (See our companion guide, Frontlit vs Backlit LED Mirrors.)
- Ignoring storage: choosing a smart mirror with no other storage nearby often means retrofitting shelving once the vanity feels cluttered.
- Measuring the wall instead of the vanity: the mirror should be sized to the benchtop, not the full wall, or it looks disconnected from the vanity beneath it.
Expert Design Tips
Designer's Golden Rules
- Size to the vanity, not the wall.
- If in doubt, choose slightly larger.
- Always centre the mirror over the vanity, not the room.
- Balance matters more than symmetry — a mirror that looks right matters more than one that measures perfectly even.
- Decide on storage before you decide on style, and match the mirror's finish to the tapware, not the vanity.
Two more principles worth applying before you order: echo a freestanding bath's curve in the mirror shape — arch or round — rather than fighting it with a hard rectangle; and if your ceiling is under 2400mm, avoid mirrors taller than about 1000mm, or they start competing with the ceiling line rather than complementing it.
Product Recommendations by Size and Shape
A quick reference for the sizing decisions above.
| Category | Recommended Product(s) | Price From |
|---|---|---|
| Round | The Amalfi, 600–1200mm | $772 NZD |
| Arch | The Positano, 600x900mm | $849 NZD |
| Arch (statement size) | The Santander, 1200–1500mm | $1,158 NZD |
| Rectangle | The Florence / The Venice, 900–1800mm | $849 NZD |
| Oval | The Riviera, 450x900mm–600x1000mm | $759 NZD |
| Organic / Irregular | The Lucca, 760x890mm–940x1090mm | $901 NZD |
| Mirror Cabinet (any shape) | Positano, Milan, Riviera, Amalfi and Lucca Cabinets | $1,738 NZD |
Frequently Asked Questions
Questions We Get Asked Most
"Can I just size up if I'm not sure?" Yes — a slightly larger mirror is almost always the safer call than one that's slightly too small.
"Do I need to match my mirror shape to my tapware?" No, but it should relate to something else in the room — a curved basin, a freestanding bath, or the vanity edge itself.
"Will a smart mirror or a mirror cabinet suit my bathroom?" It depends on storage, not style — see the decision tree above.
What size mirror should I choose for a 600mm vanity?
Look at 500–580mm for a rectangle, arch or oval mirror, or up to 600mm for a round mirror. The Amalfi (600mm round) and The Positano (600x900mm arch) both fit well.
Can my mirror be the same width as my vanity?
Yes, particularly for round, organic and cabinet styles, which are often designed to run close to full vanity width. Rectangle, arch and oval mirrors generally look better slightly narrower, at around 70–90%.
How do I size an organic or irregular mirror?
Slightly narrower than the standard rectangle rule, since an organic mirror's irregular outline carries more visual weight than its measurements suggest — it works best as a single statement piece rather than paired with a second mirror.
What if my vanity is a non-standard width, like 1050mm?
Use the same 70–90% rule and round to the nearest available size — for 1050mm, a mirror between 900mm and 950mm generally looks balanced. Sizing down slightly is safer than overhanging the benchtop.
Bathroom Mirror Buying Checklist
Save this before you order — five minutes with a tape measure now avoids a return later.
- ✓ Measure your vanity width
- ✓ Measure the height of your tapware above the benchtop
- ✓ Check your ceiling height, especially for a tall rectangle or arch mirror
- ✓ Decide whether you need extra storage, or whether your vanity already has enough
- ✓ Decide whether you want integrated lighting, and if so, which colour temperature
- ✓ Confirm your electrician has a power point positioned correctly behind or beside the mirror
- ✓ If buying a mirror cabinet, check your wall cavity depth if you're planning a recessed or semi-recessed install
The Bottom Line
Mirror sizing comes down to a handful of repeatable principles: size to the vanity, not the wall; adjust the width rule for the shape you've chosen; keep roughly 100mm of clearance above the tapware; and when in doubt, size up rather than down.
Choose proportion over trends. A well-sized mirror in a simple shape will still look right in ten years — an oversized or undersized one won't, no matter how fashionable the frame. Follow the sizing principles in this guide and you'll avoid the most common mistakes, choosing a mirror that looks balanced, functions beautifully and still feels timeless years from now.
Where to Next?
Now that you know your size and shape, here's where to shop:
- By shape: Round Mirrors, Arch Mirrors, Rectangle Mirrors, Oval & Irregular Shaped Mirrors
- No storage needed: the full Smart Mirrors range
- Need storage: the full Mirror Cabinets range
- Not sure where to start: our Best Sellers
