Room area calculator:
measure a room and order the right amount

How to find the area of a room

For a rectangular room, area is length multiplied by width, both measured in the same unit. A room 14 ft long and 11.5 ft wide has an area of 14 × 11.5 = 161 square feet.

Room area is the number behind almost every home job: how much flooring to buy, how many tiles to order, how much paint or how large an air conditioner you need. Measure once, carefully, and you can answer all of them.

This guide covers feet and metres, rooms that are not simple rectangles, and how to turn the area into a purchase quantity. Use the calculator on this page for the multiplication, and use the notes below to measure the right thing.

Room area formula and how to measure

1. 1Measure the longest wall at floor level, wall to wall, and write it down.
2. 2Measure the other dimension the same way, at right angles.
3. 3Convert inches to feet by dividing by 12: 6 in = 0.5 ft, 9 in = 0.75 ft.
4. 4Multiply the two numbers.
5. 5Measure a second time at a different height; old walls are rarely straight.

Small errors compound because you multiply two measurements. If each side of the bedroom is one inch too long, 14 ft 1 in by 11 ft 7 in gives about 163.1 sq ft instead of 161, which is roughly 2 sq ft or 1.3% too much. That is harmless for paint and costly if the floor is a premium stone sold per piece.

If the two measurements of the same wall differ by more than an inch or two, use the larger one for ordering material and the smaller one for fitting furniture.

Worked example: a bedroom of 14 ft by 11 ft 6 in

Going the other way, a room of 4.5 m by 3.2 m has an area of 14.4 m², which is 14.4 ÷ 0.09290304 ≈ 155 sq ft. The two rooms are nearly the same size, which is a handy sense check when comparing a plan drawn in metres with a quote given in feet.

Room size chart: square feet, square metres and square yards

Square yards, sometimes called gaj, are still used for plots and some flat listings. Divide square feet by 9 to convert: 144 sq ft is 16 sq yd, and a 300 sq ft room is about 33.3 sq yd.

To go from square feet to square metres, multiply by 0.0929. To go from square metres to square feet, multiply by 10.764. A rough shortcut is that 1 m² is a little under 11 sq ft.

L-shaped rooms, cut-outs and several rooms

Split the floor into rectangles, find the area of each and add them. An L-shaped room made of a 16 ft × 12 ft main part and a 6 ft × 5 ft alcove has an area of 192 + 30 = 222 sq ft, or about 20.62 m².

If a feature takes up floor you do not want to cover, subtract its area. A fixed 6 ft × 2 ft wardrobe base removes 12 sq ft, leaving 210 sq ft of exposed floor in the example above. A pillar of 1.5 ft × 1.5 ft removes 2.25 sq ft.

• Bay windows and niches: measure them as extra rectangles.
• Doorways: add the width of the opening times the wall thickness if flooring runs through it.
• Curved walls: approximate with rectangles and triangles, or measure the longest inscribed rectangle and add a margin.

For a whole-home job, measure each room separately and add the areas. A bedroom of 161 sq ft, a hall of 15 × 12 = 180 sq ft and a kitchen of 10 × 8 = 80 sq ft come to 421 sq ft, or about 39.1 m².

Do not measure the outer dimensions of the flat and multiply. That includes walls, balconies and shafts, and will overstate the floor you can cover by a surprising margin. Passages between rooms also need their own rectangle.

Keep a small sketch with the measurement of every rectangle next to it. When the supplier asks for the size again, or you need to change the order, you will not have to go back with a tape.

From area to flooring and tiles

Area is not the quantity you buy. Tiles and boards are cut at edges and some break, so add a wastage allowance of about 10%, and more for diagonal layouts or patterned tiles. For the 161 sq ft room, 161 × 1.10 ≈ 177 sq ft of material.

At an assumed ₹85 per square foot, flooring the room costs 161 × 85 = ₹13,685 for the area itself, and about ₹15,054 if you buy the extra 10% of material. These rates are only for illustration; use the price on your quote.

Mistakes people make measuring room area

• Measuring along skirting or a cupboard instead of floor to floor.
• Reading 11 ft 6 in as 11.6. Six inches is 0.5 ft.
• Multiplying feet by metres. Convert first.
• Treating carpet area and super built-up area as the same. Builders' quoted areas include walls and shared space.
• Ordering exactly the area with no allowance for cuts.

It also helps to measure with the right tool. A steel tape is accurate enough for most rooms. For long rooms, a second person to hold the end avoids sag, and a laser measure is faster when you are working alone.

Note that the floor area of a room is not its wall area. For paint you need the perimeter times the height, minus doors and windows. That is a separate calculation.