Room Size
Estimate room area and seating capacity.
About the Room Size
Floor area in square feet, for working out flooring, paint or whether the sofa fits.
How to use it
- Enter the length and width.
- Read the area in square feet.
The formula
Area is length times width. What makes a room calculation useful is what you do with the result — capacity, flooring and paint all follow from it.
Area = Length × Width
Seated capacity ≈ Area ÷ 15 sq ft per person
Standing capacity ≈ Area ÷ 7 sq ft per person
A 12 by 14 foot room is 168 square feet: about eleven people seated at tables, or roughly twenty-four standing at a reception. These densities come from event planning convention, and local fire codes may set stricter limits that always take precedence.
For an irregular room, split it into rectangles, work out each one, and add them together. A bay window or an L-shape is two or three simple calculations rather than one complicated one.
Worked examples
| Dimensions | Area | Seated at tables | Standing | Flooring with 10% waste |
|---|---|---|---|---|
| 10 × 12 ft | 120 sq ft | 8 | 17 | 132 sq ft |
| 12 × 14 ft | 168 sq ft | 11 | 24 | 185 sq ft |
| 15 × 20 ft | 300 sq ft | 20 | 42 | 330 sq ft |
| 20 × 30 ft | 600 sq ft | 40 | 85 | 660 sq ft |
The last column is the one people forget when ordering materials. Always buy about 10% more flooring than the room measures — more like 15% for diagonal layouts or patterned tile — because offcuts at the edges are unusable and a mid-job shortage means a second delivery, possibly from a different batch with a visibly different shade.
Common mistakes
- Measuring in feet and inches without converting. 12 feet 6 inches is 12.5 feet, not 12.6. Convert inches to a decimal by dividing by twelve before multiplying.
- Treating an irregular room as one rectangle. Split it into sections, calculate each, and add. Approximating an L-shaped room with a single measurement can be out by a third.
- Ordering flooring for the exact area. Cuts, waste and pattern matching mean you need more than the room measures. Ten percent is the usual minimum.
- Ignoring what the room has to hold. Capacity figures assume clear floor. Columns, a bar, a dance floor or a serving station all reduce usable area before anyone sits down.
Terms explained
- Square footage
- Area in square feet: length times width, both in feet.
- Usable area
- What remains once fixed obstructions and circulation space are removed. Always less than the raw measurement.
- Occupant load
- The maximum number of people permitted by fire code. Legally binding, and it overrides any planning rule of thumb.
- Waste factor
- Extra material ordered to cover offcuts, typically 10%, or 15% for diagonal or patterned installations.
- Circulation space
- Room to move between furniture. Event layouts generally allocate 20% to 30% of the floor to it.
- Square metres
- The metric equivalent. Divide square feet by 10.764 to convert.
Common questions
- How do I calculate the area of a room?
- Multiply length by width, both in the same unit. A 12 by 14 foot room is 168 square feet.
- How many people fit in a room?
- Roughly one per 15 square feet seated at tables, or one per 7 standing. A 168 square foot room holds about eleven seated. Fire code limits always take precedence.
- What about an L-shaped room?
- Divide it into rectangles, calculate each separately and add the results. Two simple multiplications beat one approximation every time.
- How much extra flooring should I order?
- About 10% over the measured area, or 15% for diagonal layouts and patterns. Ordering short risks a colour mismatch between batches.
- How do I convert to square metres?
- Divide square feet by 10.764. So 168 square feet is about 15.6 square metres.
- How much paint will I need?
- Paint covers wall area, not floor area. Add the wall lengths, multiply by ceiling height, subtract doors and windows, then check the coverage on the tin — usually around 350 square feet per gallon per coat.
- Does ceiling height affect capacity?
- Not for the floor-area calculation, though very low ceilings can trigger separate code restrictions and certainly affect how crowded a space feels.
- How do I measure a room with a bay window?
- Treat the main rectangle and the bay as separate areas and add them. For a curved bay, approximating it as a rectangle at its average depth is close enough for most purposes.