Mirror Math: Width, Shape & Sightlines That Flatter

In a serene, spa-like bath, the mirror isn’t an afterthought—it’s the face-framing element that makes everything feel intentional. Here’s our design math for getting it right: how wide it should be (hello ⅔ rule), where sconces actually land, and why softened shapes—pill and arched—calm all those hard tile lines.

1) Width That Works: The ⅔ Rule (and when to break it)

The rule of thumb: Choose a mirror that’s roughly ⅔ the width of your vanity. It creates balanced negative space, keeps sconces out of the corners, and flatters sightlines.

• 24” vanity → mirror ~ 16”–18”
• 30” vanity → mirror ~ 20”–22”
• 36” vanity → mirror ~ 24”
• 48” vanity → mirror ~ 32”
• 60” double → two mirrors ~ 20”–22” each (or one 40”–44” if centered with bar lighting)
• 72” double → two mirrors ~ 24”–26” each (or one 48”–52”)

When to bend the rule

• Tight walls? Go slightly narrower to keep 3–6” of breathing room on each side.
• Big, airy room? Larger mirror (¾ width) can feel luxe—just re-check sconce spacing.
• One large mirror over doubles? Great in narrow rooms; add side sconces or an above-mirror bar to avoid “bank teller” lighting.

2) Sightlines & Heights: Where the eye naturally lands

Design for real faces, not just the tape measure.

• Mirror center typically sits around 58–64” AFF (above finished floor), depending on user height.
• Top of mirror: leave 5–10” below the ceiling or crown for the room to breathe.
• Bottom of mirror: aim 4–6” above the faucet or 8–12” above the backsplash to avoid splash shadows.
• Vessel sinks: raise the mirror 2–4” to clear the taller rim without cramping the composition.

Pro move: Stand in the doorway and in front of the vanity; the top third of the mirror should capture your head and hair without cutting off the crown.

3) Sconce Spacing That Flatters (cheekbone height, always)

Nothing beats face-level, even light.

• Sconce center height: roughly 60–66” AFF (translate to cheekbone height for the primary user).
• Sconce-to-mirror spacing: keep 1.5–3” between sconce backplate/shade and mirror edge—close enough to frame the face, far enough to avoid collisions.
• Pair width: for side sconces, the inside edges should sit about 28–36” apart for typical single vanities (adjust to mirror width).
• Above-mirror bars: center around 78–82” AFF, angled to wash the face, not the ceiling.

Avoid: high overhead cans as the only light—they throw unflattering shadows.

4) Shape Therapy: Why pill & arched calm a tiled room

Tile, counters, and cabinets are all rectangles. A soft-edged mirror cuts the visual noise and feels instantly European.

Pill (rounded-rectangle)

• Best for: modern, minimal rooms; fluted or ribbed fronts.
• Effect: elongates the wall; softens without feeling thematic.
• Pair with: slim [Brass Mirrors] frames for warmth or matte black for quiet contrast.

Arched

• Best for: classic, Parisian, or Italian-warm minimalism.
• Effect: gentle “lift” above the sink; wonderful under higher ceilings.
• Watch for: sconce placement—keep shades clear of the arch’s spring point.

Rectangle

• Best for: narrow rooms needing hard lines to organize the view.
• Effect: crisp and architectural—add soft sconces or linen shades to avoid sterility.

Round

• Best for: powder rooms and small vanities.
• Effect: instant focal point; watch width (⅔ rule still applies).

5) The Tape Test (5-minute mockup before you buy)

1. Tape the vanity width on the wall at install height (or outline the actual cabinet if it’s there).
2. Mark the mirror width using the ⅔ rule; sketch top and bottom edges.
3. Dot your sconce centers at cheekbone height (60–66” AFF) and 1.5–3” off the mirror edges.
4. Take two phone pics: one from the doorway, one straight on.
5. Adjust width/height until both photos feel balanced—and the sconces aren’t crammed.

6) Comparison Grid (shape + spacing quick guide)

7) Common Misses (and easy fixes)

• Mirror too wide: Crowds sconces; drop to ⅔ and reclaim negative space.
• Sconces too high: Panda-eye shadows. Lower to cheekbone height.
• Bottom of mirror too low: Water spots and glare; raise 2–3”.
• All rectangles, no relief: Swap to pill/arched or add linen-shade sconces to soften.