Calculate Square Footage of a Room

Calculating the square footage of a room can seem intimidating if the room has a complex shape, but the process is actually fairly simple once you split the room into measurable parts. From there, all you need to do is add the square footage of each part together to find the total square footage of the room as a combined whole. Keep reading to learn more.

Steps

Essential Steps

1. Clear space along your walls. When calculating square footage of a room, you need to make sure that you can access enough space along your walls to measure the length of that wall without any obstructions.
   • Since some of the measurements will also need to be taken from the middle of the room, you may also need to move some items out from the middle. You could empty out the entire room to prevent any obstructions from getting in the way, but this is more work than you need to do. Instead, temporarily remove items from the middle of the room on an “as needed” basis to avoid putting in more effort than necessary.
2. Separate the room into simplified parts. If your room is a giant rectangle, then you do not need to split it into parts. For rooms with a more complex shape, however, you should divide the space into simplified shapes. Split it into separate rectangles, squares, triangles, and circles or semi-circles.
3. Sketch or map it out, if necessary. If you need to maintain a visual guide of your room and its measurements as you work, you can sketch a rough blueprint of the room onto paper.
   • If you do not have paper handy or would rather see a visual map within the room itself, you could separate the sections off by laying flat yardsticks or painter's tape along the invisible edges.
4. Measure and re-measure all the widths and lengths. Measure the length of each wall as well as the length of each invisible dividing line in your room. To keep matters simple, separate the space into its sections as you measure instead of writing the entire length of each wall down as one measurement.
   • After taking your initial measurements, you should re-measure each edge again to verify that your original measurements are correct. This extra step can save your project if your initial measurements were off.
   • To simplify matters, the lengths of each edge are usually rounded off to the nearest foot or half foot.
5. Calculate the area of each section. Use the basic area formulas for rectangles, triangles, and circles or semi-circles to find the area of each individual section.
   • Calculate the area of a rectangular section with A = L * W (length times width).
   • Calculate the area of a triangular section with A = 1/2 * B * H (1/2 times the base times the height).
   • Calculate the area of a circular section with A = π * r^2 (pi times the squared value of the radius).
   • Calculate the area of a semi-circular section with A = 1/2 * (π * r^2) (half the value of pi times the squared value of the radius).
6. Add the areas of each section together. Once you have the square footage of each individual section, you can find the square footage or surface area of the entire room by adding the footages of each section into a single final measurement.

Square Footage of Rectangular Sections

1. Find the length and width of the section. As indicated before, the area or square footage of a rectangular section can be found with the formula A = L * W. Use a tape measure or yardstick to find the length and width of your first rectangular section for this equation.
   • Round your measurements up to the nearest foot or half foot.
2. Multiply the two measurements together. Multiplying the length and width together is all you need to do to find the square footage of this section.
   • Example: For a rectangular section with a length of 12 feet and a width of 10 feet:
     • A = L * W = 12 * 10 = 120 sq ft
3. Repeat with any other rectangular section. If you have other rectangular or square sections of your room, measure and multiply together the length and width of each.
4. Add the sections together. Add together the square footages for each of individual section to come up with a total square footage for the entire room.
   • If your room can be divided into sections in other shapes (triangles or semi-circles), save the areas of your rectangular sections and add them to those of the other sections of your room to find the total square footage.

Square Footage of Triangular Sections

1. Find the base and height measurement of the section. As indicated before, the area or square footage of a triangular section can be found with the formula A = ½ * B * H. Use a tape measure or yardstick to find the base and height of your first triangular section.
   • Round your measurements up to the nearest foot or half foot.
2. Multiply the two measurements together. Multiply the base and height measurements together to solve the first part of the equation.
   • Example: For a triangular section with a base of 10 feet and a height of 9 feet:
     • A = 1/2 * B * H
     • B * H = 10 * 9 = 90 sq ft
3. Divide the product in half. Multiply the product of the previous step by 1/2 to find the area or square footage of that section.
   • Example: For a triangular section with a base of 10 feet and a height of 9 feet:
     • A = 1/2 * B * H = ½ * 90 = 45 sq ft
4. Repeat with any other triangular section. For any other triangular section of the room, measure and multiply together the base and height of the section. Multiply this value by 1/2 to determine the footage of that section.
5. Add the sections together. Add together the square footages for each of individual section to come up with a total square footage for the entire room.
   • If your room can be divided into sections in other shapes (rectangles or semi-circles), save the areas of your triangular sections and add them to those of the other sections of your room to find the total square footage.

Square Footage of Circular or Semi-Circular Sections

1. Find the radius of the section. As indicated before, the area or square footage of a circular section can be found with the formula A = π*r^2. If finding the area of a semi-circle, that formula becomes A = 1/2 * (π*r^2). Use a tape measure or yardstick to find the radius of your first circular or semi-circular section.
   • Round your measurement up to the nearest foot or half foot.
2. Square the measurement. Complete the first part of your equation for area by squaring the radius of your section, or multiply the measurement by itself.
   • For a circular or semi-circular section with a radius of 5.5 feet:
     • A = π * r^2
     • r^2 = 5.5 * 5.5 = 30.25 sq ft
3. Multiply by pi. Complete the area measurement for a circular space simply by multiplying the squared value of the radius by π, 3.14.
   • For a circular or semi-circular section with a radius of 5.5 feet:
     • A = π * r^2 = 3.14 * 30.25 = 95 sq ft
4. Split this product in half, if necessary. If dealing with a semi-circle instead of a full circle, you will need to complete the area measurement by cutting the previous value in half, or multiplying it by 1/2.
   • For a semi-circular section with a radius of 5.5 feet:
     • A = (1/2) * π * r^2 = (1/2) * 95 = 47.5 sq ft
5. Repeat with any other circular section. For any other circular or semi-circular section, measure and square the radius and multiply this value by π (3.14). If the section is semi-circular, cut this area measurement in half.
6. Add the sections together. Add together the square footages for each of individual section to come up with a total square footage for the entire room.
   • If your room can be divided into sections in other shapes (triangles or rectangles), save the areas of your circular or semi-circular sections and add them to those of the other sections of your room to find the total square footage.

Example

1. Split the room into measurable sections. Measure the straight edges of each section. For the purpose of this example, consider a room that is divided into three rectangular sections, two triangular sections, and one semi-circular section.
   • The largest part of the room is a rectangle. Off the top and right sides of this rectangle are smaller rectangular sections extending the full length of the wall without connecting. A triangle connects off the right-side rectangle, spanning the rectangle's length, and a smaller triangle connects to a portion of the top section. A final semi-circular section lies along part of the bottom of the center rectangle in the room.
   • The large rectangle measures 12 feet by 10 feet.
   • The smaller top rectangle measures 12 feet by 2 feet.
   • The smaller right rectangle measures 10 feet by 3 feet.
   • The larger triangle has a base of 10 feet and a height of 9 feet.
   • The smaller triangle has a base of 5 feet and a height of 7.5 feet.
   • The semi-circle has a radius of 5.5 feet.
2. Find the area of each rectangular section. Multiply the lengths and widths of each section to find the square footage of each individual section.
   • Section 1 = 12 * 10 = 120 sq ft
   • Section 2 = 12 * 2 = 24 sq ft
   • Section 3 = 10 * 3 = 30 sq ft
3. Find the area of each triangular section. Multiply the base and height of each section together. Find the area of each section by multiplying this value by 1/2.
   • Section 4 = (1/2) * 10 * 9 = (1/2) * 90 = 45 sq ft
   • Section 5 = (1/2) * 5 * 7.5 = (1/2) * 37.5 = 18.75 sq ft
4. Find the area of the semi-circular section. Square the radius of this section and multiply by pi, or 3.14. Multiply this value by 1/2 to find the area of the semi-circle.
   • Section 6 = (1/2) * π * 5.5 * 5.5 = (1/2) * 3.14 * 30.25 = 95 (rounded up from 94.985) * (1/2) = 47.5 sq ft
5. Add the areas together to find the total square footage of the room. Combine the surface area of the three rectangular sections, two triangular sections, and one semi-circular section. This sum will give you the square footage of the room.
   • Total square footage = 120 + 24 + 30 + 45 + 18.75 + 47.5 = 285.25 sq ft

Things You'll Need

• Tape measure or yardstick
• Pencil
• Paper
• Calculator
• Painter's tape (optional)

Sources and Citations

See also

• Install Reflective Tape
• Decoupage a Table
• Use an Ammeter
• Use a Vernier Caliper
• Build a Sound Proof Room
• Measure for Stairs
• Level an Existing House
• Measure Carpet
• Read a Ruler
• Measure Centimeters

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