Do I deduct the whole door?

Yes: deduct the full opening. It's standard practice in paint measurement.

How do I measure a room for painting?

Measure length × height per wall, add, and deduct doors (≈22 sq ft) and windows. A 13×10 ft room at 8 ft high is about 355 sq ft net.

Only if you paint it; measure other finishes separately.

Do I deduct built-in closets?

Yes if you won't paint them: every unpainted square foot saves material.

Can I work in square feet?

Yes — switch to Imperial above the form. A 35 m² room shows as ≈377 sq ft, and the math stays identical.

Wall & ceiling area calculator

Adds walls (length × height), includes the ceiling if you paint it, and subtracts openings. The basis for paint, drywall and wallpaper.

Purchase quantity

90.417 ft²

Net measurement: 86.111 ft² · Waste 5 %

Area to cover90.417 ft²

Use my prices

Your prices per language/currency. Used when you enable “Use my prices” in calculators. My prices →

Calculate labour, margin & GST

How it's calculated (visible formula)

net = Σ(length × height) + ceiling − openings; buy = net × (1 + waste)

Net geometric measurement, no waste.
Adjustable waste % for cuts and breakage.
Purchase rounded up to sellable units (boxes, bags, buckets, boards).

See methodology and formula versions

Worked example: Room 4×3 m, 2.5 m high

Walls: 2×(4×2.5) + 2×(3×2.5) = 35 m²
Openings: 2 m² door
Net: 33 m²

→ 33 m² net (34.65 m² with a 5% measuring margin).

Common mistakes

Measuring the perimeter and forgetting to multiply by height.
Not deducting closets you won't paint.
Mixing m and cm in one calculation.

From calculation to quote

Add labour, overhead and your margin, and generate the professional PDF.

Create quote Calculate margin & GST

FAQs

Do I deduct the whole door?: Yes: deduct the full opening. It's standard practice in paint measurement.
How do I measure a room for painting?: Measure length × height per wall, add, and deduct doors (≈22 sq ft) and windows. A 13×10 ft room at 8 ft high is about 355 sq ft net.
Include the ceiling?: Only if you paint it; measure other finishes separately.
Do I deduct built-in closets?: Yes if you won't paint them: every unpainted square foot saves material.
Can I work in square feet?: Yes — switch to Imperial above the form. A 35 m² room shows as ≈377 sq ft, and the math stays identical.

Maintained by Srikanta M · Formula v1.0.0 · Verified 2026-09-10 · Updated 2026-09-10 · Limits: quantity estimation, not structural design or site supervision.