How Many Square Feet Is a 18x20 Room?
A 18 ft × 20 ft room equals 360 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 18x20 Room
| Metric | Value |
|---|---|
| Floor area | 360 sq ft |
| Floor area (m²) | 33.45 m² |
| Floor area (sq yd) | 40.00 sq yd |
| Perimeter | 76 ft |
| Wall area (8 ft ceiling) | 608 sq ft |
| Wall area (9 ft ceiling) | 684 sq ft |
| Wall area (10 ft ceiling) | 760 sq ft |
Common Uses for a 18x20 Space
- family great room
At 360 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' × 20' room, buy enough flooring to cover 360 sq ft plus a waste allowance:
| Flooring Type | Waste % | Buy This Much |
|---|---|---|
| Laminate / LVP (plank) | 10% | 397 sq ft |
| Hardwood | 10% | 397 sq ft |
| Ceramic tile (straight) | 10% | 397 sq ft |
| Ceramic tile (diagonal) | 15% | 414 sq ft |
| Carpet | 10% | 397 sq ft (45 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 18x20 Room?
With 8 ft ceilings you'll paint about 608 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 18x20 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 18x20 Room?
At typical US rates of $150–$300 per sq ft for new construction, a 18x20 addition would cost roughly $54,000–$108,000. For remodels:
- Basic flooring replacement: $1,080–$3,600
- Mid-range remodel: $18,000–$36,000
- Full gut renovation: $36,000–$90,000
Refine with our Cost per Square Foot Calculator.
Frequently Asked Questions
How many square feet is 18x20?
18 × 20 = 360 square feet.
How many square meters is 18x20?
33.45 m².
How many tiles will fit in a 18x20 room?
Depends on tile size. 12"×12" tiles = 397 tiles (with 10% waste). See our Tile Calculator for 6", 18", and 24" sizes.
How much carpet do I need for a 18x20 room?
40.00 sq yd minimum, or 44.00 sq yd with 10% waste for cuts and seams.