Triangle Square Feet Calculator
Total Area
Total Price
Triangle Diagram
InteractiveHow to Calculate Square Feet of a Triangle
Every triangle — whether it forms a gable roof, an oddly shaped room corner, or a wedge of yard space — obeys two core area formulas. Pick the one that matches the measurements you already have. For layouts that combine several triangles and rectangles, switch to the irregular shape area calculator, measure a plot with the land area calculator, size a single room, or head back to the main square footage calculator.
Base × Height Method
The most common approach: multiply the base length by the perpendicular height, then divide by two. The perpendicular height is the straight-line distance from the base to the opposite vertex, measured at a 90-degree angle to the base.
Triangle Area Formula
FormulaExample: A triangle with a 20 ft base and 10 ft height = ½ × 20 × 10 = 100 sq ft
Step-by-Step Visual Breakdown
VisualHeron's Formula (Three Sides Known)
When you know all three side lengths but not the height, Heron's formula handles it. First, find the semi-perimeter (half the sum of all three sides). Then plug into: Area = √[s(s−a)(s−b)(s−c)]. This approach works for any triangle, regardless of shape.
Right Triangle Shortcut
For right triangles, the two sides forming the 90-degree angle act as base and height. Multiply them and divide by two — no extra height measurement needed.
Most Common Triangle Square Footage Examples
Click any example below to auto-load values into the calculator above and see the interactive diagram update in real time.
Triangle Roof & Gable Calculator Examples
Triangular roof sections — especially gable ends — are the most common real-world triangle calculations. Below are worked examples for gable area, siding estimation, and paint coverage. Click any example to load it into the main calculator. For full roof square footage calculations, use our dedicated roof calculator.
How to Calculate Triangular Gable Square Footage
DiagramTriangular Room Flooring Example
Bay windows, angled hallways, and attic rooms under roof pitches often create triangular floor sections. Knowing the exact square footage prevents over-ordering — and the waste factor matters more here because angled cuts generate more offcuts. Use our flooring calculator for rectangular rooms, or the cost calculator for material budgeting.
Flooring Estimate — Bay Window Alcove
InteractiveFlooring Material Estimates for 30 sq ft Triangle
Hardwood
30 sq ft + 15% waste = 34.5 sq ft needed. At $8/sq ft installed → $276
Tile
30 sq ft + 20% waste = 36 sq ft needed. At $6/sq ft installed → $216
Laminate
30 sq ft + 12% waste = 33.6 sq ft needed. At $4/sq ft installed → $134
Carpet
30 sq ft + 10% waste = 33 sq ft needed. At $5/sq ft installed → $165
Land Area Triangle Example
Corner lots, pie-shaped parcels, and triangular fields are common in suburban and rural areas. Accurately calculating the area of triangular land determines property value, fencing requirements, and landscaping budgets. For full property area calculations, see our land area calculator.
Triangular Corner Lot — 150 ft × 200 ft
Land SurveyCommon Triangle Sizes & Square Footage Table
Quick reference table for frequently encountered triangle dimensions. All values use the standard ½ × Base × Height formula. Click any row to load it into the calculator above.
| Base (ft) | Height (ft) | Sq Feet | Sq Yards | Sq Meters | Common Use |
|---|---|---|---|---|---|
| 4 | 3 | 6 | 0.67 | 0.56 | Small shelf / bracket |
| 6 | 4 | 12 | 1.33 | 1.11 | Garden corner |
| 8 | 6 | 24 | 2.67 | 2.23 | Bay window alcove |
| 10 | 8 | 40 | 4.44 | 3.72 | Dormer wall |
| 12 | 8 | 48 | 5.33 | 4.46 | Small gable end |
| 15 | 10 | 75 | 8.33 | 6.97 | Deck triangle |
| 20 | 8 | 80 | 8.89 | 7.43 | Standard gable |
| 24 | 8 | 96 | 10.67 | 8.92 | Wide gable / siding |
| 24 | 12 | 144 | 16.00 | 13.38 | Steep roof gable |
| 30 | 10 | 150 | 16.67 | 13.94 | Large gable / A-frame |
| 36 | 18 | 324 | 36.00 | 30.10 | A-frame cabin wall |
| 40 | 15 | 300 | 33.33 | 27.87 | Commercial gable |
| 50 | 30 | 750 | 83.33 | 69.68 | Barn end wall |
| 100 | 80 | 4,000 | 444.44 | 371.61 | Triangular yard section |
| 150 | 200 | 15,000 | 1,666.67 | 1,393.55 | Corner lot |
Triangle Size Visual Comparison
To ScalePractical Uses for Triangle Square Footage
Roofing and Gable Ends
A gable end is a triangle sitting above the flat wall line. Measuring the span (base) and the peak height gives you the area for siding, insulation, or paint estimation. Contractors routinely calculate square feet of triangular gable sections before quoting roofing materials.
Landscaping and Odd Lot Sections
Corner lots and pie-shaped parcels often contain triangular zones. Calculate the triangle area separately, then add it to any rectangular sections to get your total property square footage.
Architectural Features
Dormer windows, A-frame walls, and cathedral ceilings all involve triangular surfaces. Knowing the square feet of these sections prevents over-ordering drywall, tiles, or cladding.
Flooring Cuts and Waste Planning
Bay windows and angled hallways create triangular floor areas. Calculating these zones accurately helps you buy the right amount of flooring material and anticipate cutting waste.
Triangle Types and Their Square Feet Calculation
Equilateral Triangle
All three sides are equal. The height equals (√3 / 2) × side length. So the area formula simplifies to: Area = (√3 / 4) × side². For a 10 ft equilateral triangle, area = 43.30 sq ft.
Isosceles Triangle
Two sides are equal. Calculate the height using the Pythagorean theorem: height = √(equal_side² − (base/2)²). Then use the standard ½ × base × height formula.
Scalene Triangle
All sides differ. Heron's formula is the go-to method here since determining the height geometrically requires extra construction lines. Input all three sides and the calculator handles the rest.
Right Triangle
The two legs (non-hypotenuse sides) serve as base and height. Area = ½ × leg₁ × leg₂. The simplest triangle to calculate.
How to Measure a Triangle for Square Feet
Step 1: Identify the Base
Any side of the triangle can serve as the base. For roof triangles, the base is usually the bottom edge (the wall span). For lot measurements, pick the side you can measure most easily with a tape.
Step 2: Measure the Height
The height must be perpendicular to your chosen base. Drop a vertical line from the opposite corner straight down to the base line. For roofs, this is the ridge height above the wall plate.
Step 3: Apply the Formula
Multiply base × height, then divide by 2. Convert units if needed — our calculator handles mixed units automatically. If your base is in feet and height is in inches, enter each in its native unit and the tool converts everything to square feet.
Specialized Square Feet Calculators
Each tool is purpose-built with its own dedicated calculator, visual diagrams, and step-by-step guidance.
Triangle
Find the area of any triangle using base × height or Heron's formula with three side lengths.
Irregular Shape
Break any complex shape into rectangles and triangles. Add sections and sum them automatically.
Inches
Enter measurements in inches and get instant square feet results. Includes a quick-reference conversion table.
From Meters
Convert metric measurements to square feet. Perfect for international real estate and imported materials.
Linear Feet
Convert linear footage to square feet for lumber, carpet, fencing, decking, and rolled materials.
Sq Meters
Convert sq ft to sq m with live dual display. Essential for international real estate and architecture.
Sq Yards
Divide sq ft by 9 to get sq yd. Perfect for carpet ordering, sod purchases, and fabric estimates.
Acres
Convert property area from sq ft to acres. Ideal for land sales, farming, zoning, and lot size comparisons.
Cubic Feet
Add depth to any area to calculate volume. Essential for concrete, mulch, soil, gravel, and pool planning.
House
Add rooms one by one and get your home's total square footage, with a live bar chart breakdown per room.
Room
Measure rectangular or L-shaped rooms for flooring, paint, and renovation budgeting with instant cost estimates.
Wall
Get net wall area for paint, wallpaper, or tile by subtracting doors and windows from the gross surface.
Tile
Enter room size and tile dimensions to calculate tile count, boxes to buy, and total material cost including waste.
Concrete
Get slab area, cubic yards of concrete, bags needed, and pour cost for any project.
Land
Measure any property lot or parcel in sq ft and acres. Supports rectangular, triangular, and irregular shapes.
BTU Calculator
Calculate heating and cooling BTU needs per square foot based on climate zone, ceiling height, and insulation.
Cost
Estimate total project cost from area and price per square foot. Compare scenarios with tax and markup.
Flooring
Find exact flooring material for hardwood, laminate, vinyl, or carpet with waste factor and box count.
Roof
Get true roof surface area using pitch multiplier. Includes roofing squares, shingle bundles, and cost.
Paint Area
Get paintable wall area with door and window deductions. Calculates gallons, coats, and total paint cost.
Estimation
Add multiple areas, apply buffer percentages, and get quick estimates for budgeting any project.
Related Calculators
Explore other free square footage and cost tools:
Frequently Asked Questions
To calculate triangle square footage, multiply the base of the triangle by its perpendicular height and divide the result by two. Alternatively, if you know all three side lengths, you can use Heron's formula.
The square footage of a triangle is the total surface area enclosed by its three sides, calculated in square feet.
Multiply the base by the perpendicular height and divide by two. For example, a triangle with a 15 ft base and 10 ft height has an area of 75 square feet (15 × 10 ÷ 2).
Heron's formula calculates area from three side lengths. First find the semi-perimeter: s = (a + b + c) / 2. Then Area = √[s × (s−a) × (s−b) × (s−c)]. It works for every triangle shape.
Yes. Calculate the area in square inches first (½ × base_in × height_in), then divide by 144 to convert to square feet. Our calculator handles this conversion automatically.
Area = ½ × 20 × 15 = 150 square feet.
The height (also called altitude) is the perpendicular distance from the base to the opposite vertex. A side length is the edge of the triangle. They're only the same in a right triangle where one leg acts as the height.
Measure the base (the span of the gable wall) and the height (from the wall plate to the peak). Use ½ × base × height. For pitched roof surfaces, measure the actual rafter length instead for the sloped surface area.
Yes. The ½ × base × height formula works universally for equilateral, isosceles, scalene, and right triangles — as long as you use the correct perpendicular height for your chosen base.
If you can measure all three boundary lengths, use Heron's formula. If you can identify a base and drop a perpendicular from the opposite corner, use the ½ × base × height method. For very irregular lots, a surveyor's GPS measurements paired with Heron's formula gives the most accurate result.
Calculate the triangle's square footage, then add 10–15% for cutting waste. Triangular sections require angled cuts, which generate more offcuts than rectangular rooms.