Size your vanity
Wall length and who uses it. Heights follow from the user.
How this calculator works
- Usable width = wall length − 8 in, allowing four inches of clearance at each end so the vanity does not jam against the walls.
- Width = the smaller of the usable width and the target — 36 in for one basin, 66 in for two.
- Basin rim height = 0.52 × user height, rounded to the nearest centimetre and clamped to 76–95 cm.
- Counter height = rim height, less 12 cm where a counter-top bowl is selected, because the bowl sits proud of the counter.
- Depth follows the basin type: 21 in undermount, 22 in counter-top, 18 in wall-hung.
- Mirror = vanity width − 4 in by 36 in high, with the bottom edge 8 inches above the counter.
| User height | Basin rim | With undermount basin | With counter-top bowl |
|---|---|---|---|
| 150 cm | 78 cm | 78 cm counter | 76 cm counter (clamped) |
| 158 cm | 82 cm | 82 cm counter | 76 cm counter (clamped) |
| 165 cm | 86 cm | 86 cm counter | 74 → 76 cm counter |
| 173 cm | 90 cm | 90 cm counter | 78 cm counter |
| 182 cm | 95 cm | 95 cm counter | 83 cm counter |
A counter-top bowl always forces a lower counter, which is why it works badly in a bathroom shared by adults and small children — the counter becomes too low for one and the rim too high for the other.
Design and build under one accountable roof
Worked example — the default vanity
| Step | Arithmetic | Result |
|---|---|---|
| Wall available | 6 ft | 72 in |
| Usable width | 72 − 8 | 64 in |
| Target for two basins | 66 in | limited to 64 in |
| Two basins possible | 64 ≥ 60 | Yes, 30 in each |
| Basin rim height | 0.52 × 165 | 86 cm |
| Counter height, undermount | same as rim | 86 cm |
| Depth | undermount | 21 in |
| Mirror | 64 − 4 by 36 in | 60 × 36 in |
| Mirror bottom edge | 34 + 8 | 42 in from floor |
Details that decide whether a vanity survives
A bathroom vanity lives in the wettest, most humid joinery position in the flat, and most of them fail from the bottom up. Three specifications prevent it. The carcass should be BWP plywood or WPC, not MR ply and never particle board. The end grain of every panel must be sealed before the laminate goes on, because that is where water wicks in. And the vanity should ideally be wall-hung, off the floor by 100–150 mm, so that mopping never puts the plinth in standing water.
The second area is the plumbing. A drawer under a basin has to be U-cut around the bottle trap, which is ordinary joinery work but has to be drawn before fabrication — a drawer box delivered square and then cut on site is never as neat. Ask for the trap position on the drawing. And specify an angle valve and a flexible connector rather than a hard-piped tap, so the vanity can be removed in future without cutting pipework.
Third, the mirror. A mirror should be at least as wide as the basin below it and ideally the full vanity width less a few inches, with its bottom edge about eight inches above the counter so splash does not reach it. Lighting goes at the sides at face height, not above — a downlight over a mirror throws the face into shadow, which is why bathroom photographs taken under one always look unflattering.
Every constant on this page comes from Greenbox site records — measured drawings, signed BOQs and completion certificates from projects delivered between 2023 and 2026 — rounded to the figures an estimator would actually write down. We publish them so the arithmetic can be audited rather than trusted. Treat the output as a planning figure: accurate enough to brief a landlord, a bank or a family, and not accurate enough to sign a contract against.
What this tool does not cover
- Plumbing position. The water and waste points are usually fixed, and a vanity more than about 2 ft from them needs pipework re-run.
- Counter material and cut-outs — see the countertop area calculator.
- Wall-hung vanity brackets and the backing plate they need, which must go in before tiling.
- Mirror cabinets, which are deeper than a plain mirror and project into the standing space.
- Accessibility requirements, which need knee clearance under the basin and a different height entirely.
- For whether the vanity fits at all, use the bathroom layout planner.
Selected work by Greenbox Design Studio. Tap any image to enlarge.
Frequently asked questions
What is the standard bathroom vanity height?+
Indian builders install at 80 cm, which suits a user of about 154 cm. A better rule is 52% of the user's height — 86 cm for a 165 cm adult and 90 cm for a 173 cm one. It costs nothing to change at drawing stage.
How wide should a double vanity be?+
Sixty inches minimum, which gives 30 inches per person. Below that, two basins are cramped and a single wide basin with generous counter on both sides is more usable. Sixty-six to seventy-two inches is comfortable.
How deep should a bathroom vanity be?+
Twenty-one inches for an undermount basin, 22 for a counter-top bowl and 18 for a wall-hung unit. Deeper than 22 inches puts the tap out of comfortable reach and takes standing space out of a small bathroom.
Should a vanity be wall-hung or floor-standing?+
Wall-hung, wherever the wall can take it. Lifting the carcass 100–150 mm off the floor keeps the plinth out of standing water, makes the floor easier to clean and makes a small bathroom look larger. It needs a backing plate fixed before tiling, so decide early.
How big should a bathroom mirror be?+
At least as wide as the basin, and ideally the vanity width less four inches. Thirty-six inches high is standard, with the bottom edge about eight inches above the counter. Light it from the sides at face height, not from above.