How Many Square Feet Is a 18x18 Room?
A 18 ft × 18 ft room equals 324 square feet. Use the calculator below to double-check or customize with waste and cost.
Last updated:Tip: If you only have the diameter, divide by 2 to get the radius.
L-shape = two rectangles sharing a corner.
Add one row per rectangle and we'll sum them.
Key Measurements for a 18x18 Room
| Metric | Value |
|---|---|
| Floor area | 324 sq ft |
| Floor area (m²) | 30.10 m² |
| Floor area (sq yd) | 36.00 sq yd |
| Perimeter | 72 ft |
| Wall area (8 ft ceiling) | 576 sq ft |
| Wall area (9 ft ceiling) | 648 sq ft |
| Wall area (10 ft ceiling) | 720 sq ft |
Common Uses for a 18x18 Space
- great room
- master suite
At 324 sq ft, this falls in the large category — sized for great rooms, master suites, or single-car garages.
How Much Flooring Will You Need?
For a 18' × 18' room, buy enough flooring to cover 324 sq ft plus a waste allowance:
| Flooring Type | Waste % | Buy This Much |
|---|---|---|
| Laminate / LVP (plank) | 10% | 357 sq ft |
| Hardwood | 10% | 357 sq ft |
| Ceramic tile (straight) | 10% | 357 sq ft |
| Ceramic tile (diagonal) | 15% | 373 sq ft |
| Carpet | 10% | 357 sq ft (40 sq yd) |
Need an exact estimate? Use our Flooring Calculator for plank count, or the Tile Calculator for boxes of tile.
How Much Paint for a 18x18 Room?
With 8 ft ceilings you'll paint about 576 sq ft of wall. A gallon covers ~350 sq ft, so you'll need 2 gallons per coat. Plan on two coats for a color change.
Detailed breakdown on our Paint Calculator.
Is a 18x18 Room Big?
This is a large room — great for primary suites, family rooms, or open-plan spaces.
How Much Does It Cost to Build a 18x18 Room?
At typical US rates of $150–$300 per sq ft for new construction, a 18x18 addition would cost roughly $48,600–$97,200. For remodels:
- Basic flooring replacement: $972–$3,240
- Mid-range remodel: $16,200–$32,400
- Full gut renovation: $32,400–$81,000
Refine with our Cost per Square Foot Calculator.
Frequently Asked Questions
How many square feet is 18x18?
18 × 18 = 324 square feet.
How many square meters is 18x18?
30.10 m².
How many tiles will fit in a 18x18 room?
Depends on tile size. 12"×12" tiles = 357 tiles (with 10% waste). See our Tile Calculator for 6", 18", and 24" sizes.
How much carpet do I need for a 18x18 room?
36.00 sq yd minimum, or 39.60 sq yd with 10% waste for cuts and seams.