Triangle Square Footage Calculator: How to Find Sq Ft

This calculator works out the area of a triangle in square feet (sq ft) when you know its base and height. You enter the base length and the height (measured at a right angle to the base), and it returns the area in square feet, along with the same area in square meters for convenience. The formula is simple: area = ½ × base × height.

Formula

The area of a triangle is given by:

Area = ½ × base × height

Where:

• base (b) – the length of one side of the triangle, in feet (ft).
• height (h) – the perpendicular distance from that base to the opposite vertex (the highest point), also in feet (ft).
• Area – the result, in square feet (sq ft).

If you measure in inches, convert to feet first by dividing by 12. If you measure in meters, multiply the result by 10.7639 to get square feet.

Worked Example

Using the default values from the calculator above (base = 10 ft, height = 6 ft):

1. Multiply the base by the height: 10 × 6 = 60
2. Divide by 2: 60 ÷ 2 = 30
3. The area is 30 square feet.

In square meters: 30 × 0.092903 = 2.79 m² (rounded to two decimals). This matches the calculator’s output.

When to Use This Calculator

You need the base and height method when you can identify a side (the base) and measure the straight-line distance from that side up to the opposite corner. This is the most common way to measure a triangle in real life – for example:

• Flooring or tiling a triangular room or patio.
• Estimating the area of a triangular garden bed or lawn.
• Calculating the amount of paint or sealant for a triangular wall.
• Ordering sod, mulch, or gravel for a triangular plot.

If you have a right triangle, the two shorter sides are the base and height, so you can multiply them and divide by 2 directly.

How to Read the Result

The result is the flat area inside the triangle, expressed in square feet. One square foot is a square that is 1 foot on each side. For example, a triangle with a 10 ft base and 6 ft height covers the same floor area as thirty 1-foot squares.

If you need square yards (for carpet or sod), divide the square footage by 9. If you need square meters, multiply by 0.092903. The calculator already gives you square meters as a secondary output.

Common Mistakes and How to Avoid Them

• Using a slanted side as the height. The height must be perpendicular (at a 90° angle) to the base. If you measure along the side, you will get a wrong, usually larger, number.
• Mixing units. If the base is in feet and the height is in inches, convert the inches to feet first. For example, 6 inches = 0.5 ft.
• Forgetting to divide by 2. The most common error – the area of a triangle is half the area of a rectangle with the same base and height.
• Using the wrong formula for a non-triangular shape. This calculator only works for triangles. If your shape has four sides, use a rectangle or trapezoid formula instead.

Limitations of the Base–Height Formula

This formula works for any triangle – acute, obtuse, or right – as long as you know the base and the perpendicular height. However, in some situations you may not know the height. For example, if you only know the lengths of all three sides, you need Heron’s formula:

Area = √(s(s−a)(s−b)(s−c)), where s = (a+b+c)/2.

If you know two sides and the angle between them, use: Area = ½ × a × b × sin(θ).

For a typical home project, measuring the base and height with a tape measure is usually the easiest. But for irregular land plots, you may need the more advanced formulas.

Frequently Asked Questions

How do I calculate square feet of a triangle if I only know the three sides?

Use Heron’s formula. First, add all three sides and divide by 2 to get the semiperimeter (s). Then compute s × (s−a) × (s−b) × (s−c) and take the square root. The result is in square feet if the side lengths are in feet.

What if my triangle is not a right triangle?

It doesn’t matter. The base–height formula works for every type of triangle, as long as the height is measured perpendicular to the base. You can choose any side as the base; just measure the height from that side to the opposite corner.

Can I use this calculator for a triangular room?

Yes. Measure the longest wall as the base, then measure from that wall straight across to the opposite corner (making sure the tape is perpendicular to the wall). That’s the height. Enter both in feet.

How do I convert inches to feet for the base and height?

Divide the number of inches by 12. For example, 18 inches = 1.5 feet. If you have a measurement like 5 ft 6 in, convert the 6 inches to 0.5 ft, so the total is 5.5 ft.

What is the difference between square feet and square meters?

They are both units of area. One square meter is about 10.764 square feet. To convert square feet to square meters, multiply by 0.092903. The calculator does this for you in the second output.

Related

• Trapezoid Area Formula Calculator
• OD600 Cell Number Converter
• Degree to Angle Converter: Minutes, Radians & More

in b | Base length | ft | 10 | 0
in h | Height (perpendicular) | ft | 6 | 0
out area_sqft | Area | sq ft | 0.5 * b * h | 2
out area_sqm | Area | sq m | 0.5 * b * h * 0.092903 | 2