Room Size Calculator
A room dimension calculator for every measurement a project needs: a 14 × 12 ft room with an 8 ft ceiling is 168 sq ft of floor, 52 ft around and 1,344 cu ft of air.
Quick reference
Room Measurements for Common Room Sizes
Each room with an 8 ft ceiling, one door and two windows. Use the calculator above for your own room.
| Room | Floor area | Floor area (m²) | Perimeter | Wall area | Volume |
|---|---|---|---|---|---|
| 10 × 8 ft | 80 sq ft | 7.43 m² | 36 ft | 237 sq ft | 640 cu ft |
| 10 × 10 ft | 100 sq ft | 9.29 m² | 40 ft | 269 sq ft | 800 cu ft |
| 12 × 10 ft | 120 sq ft | 11.15 m² | 44 ft | 301 sq ft | 960 cu ft |
| 12 × 12 ft | 144 sq ft | 13.38 m² | 48 ft | 333 sq ft | 1,152 cu ft |
| 14 × 12 ft | 168 sq ft | 15.61 m² | 52 ft | 365 sq ft | 1,344 cu ft |
| 16 × 14 ft | 224 sq ft | 20.81 m² | 60 ft | 429 sq ft | 1,792 cu ft |
| 20 × 16 ft | 320 sq ft | 29.73 m² | 72 ft | 525 sq ft | 2,560 cu ft |
| 20 × 20 ft | 400 sq ft | 37.16 m² | 80 ft | 589 sq ft | 3,200 cu ft |
Wall area is the four walls minus a typical 3 × 7 ft door (21 sq ft) and two 3 × 5 ft windows (15 sq ft each).
Ceiling height
Room Volume by Ceiling Height (12 × 12 ft Room)
The floor stays the same; the walls and the air volume grow with every foot of ceiling height.
| Ceiling | Volume | Volume (m³) | Wall area | Paint, 2 coats |
|---|---|---|---|---|
| 8 ft | 1,152 cu ft | 32.62 m³ | 333 sq ft | 1.9 gal |
| 9 ft | 1,296 cu ft | 36.7 m³ | 381 sq ft | 2.2 gal |
| 10 ft | 1,440 cu ft | 40.78 m³ | 429 sq ft | 2.5 gal |
| 12 ft | 1,728 cu ft | 48.93 m³ | 525 sq ft | 3 gal |
Paint at 350 sq ft per gallon per coat. Check the coverage printed on your can.
All Your Room Measurements in One Place
Area and perimeter
Length × width is the floor area (and the ceiling). Twice the length plus twice the width is the perimeter — the baseboard run, minus 3 ft for each door.
Measure a roomWall area for paint
Unfold the walls and they make one strip as long as the perimeter and as tall as the ceiling. Take off 21 sq ft per door and 15 sq ft per window, and you have the area to paint.
Work out paintRoom volume in cubic feet
Floor area × ceiling height is the room volume — what a heater, air purifier or dehumidifier is sized against. A 12 × 12 ft room holds 1,152 cu ft at 8 ft and 1,296 cu ft at 9 ft.
Standard ceiling heightsFlooring with waste
Planks and tiles are cut at the walls, and the offcuts don’t always fit elsewhere. The calculator adds 10% to the floor area — more for diagonal or herringbone layouts.
Try a new floorHow to Measure a Room
- 1
Measure length and width
Run a tape along the floor from wall to wall, at baseboard height, on the two longest walls. If the two readings differ, use the larger one.
- 2
Measure the ceiling height
Measure from the finished floor to the ceiling in a corner. Vaulted or sloped ceilings need an average of the low and high points.
- 3
Count doors and windows
Count every door and window on the walls you will paint. Enter the numbers and the calculator removes typical openings from the wall area.
What Room Measurements Are For
Painting and flooring
A 14 × 12 ft room has about 365 sq ft of wall to paint — 2.1 gal for 2 coats, so 3 gallons — and needs 184.8 sq ft of flooring with waste.
Furniture and layout
Knowing the exact room size tells you whether a sofa, bed or desk fits with walkways to spare — and lets you draw a furnished layout to scale.
Comparing rooms
Is your bedroom small, average or large? Compare your measurements with typical sizes for each type of room in a house.
FAQ
Room Measurement Questions
Multiply the length by the width in the same unit. A 14 × 12 ft room is 168 sq ft, or 15.61 m². For L-shaped rooms, split the floor into rectangles and add them — the square footage calculator does that for you.
Multiply length × width × ceiling height. A 12 × 12 ft room with an 8 ft ceiling has 1,152 cu ft (32.62 m³); raise the ceiling to 9 ft and it is 1,296 cu ft.
Add the four wall widths to get the perimeter, multiply by the ceiling height, then subtract about 21 sq ft per door and 15 sq ft per window. Divide by 350 sq ft per gallon for each coat.
There is no single standard: a 10 × 10 ft room is 100 sq ft, a 12 × 12 ft room 144 sq ft. Bedrooms, kitchens and living rooms each have their own typical range — see the types of rooms guide for sizes by room.
With an 8 ft ceiling, one door and two windows, the walls are about 333 sq ft. Two coats at 350 sq ft per gallon is 1.9 gal, so 2 gallons. Ceilings are extra.
Either. Switch the calculator to the unit on your tape; every result is shown in that unit with the other one beside it, converted from the exact figure.
About 10% over the floor area for straight-laid planks or tile, which the calculator adds. Diagonal, herringbone or large-format tile can need 15% or more; check the installer’s recommendation.