Trapezoid Area Calculator lets you quickly find the area of any trapezoid using base lengths and height — or all four sides for irregular shapes.
Get instant, accurate results in square inches, feet, centimeters, and meters — ideal for geometry, land plots, and design measurements.
Trapezoid Area Calculator – bases & height or bases & legs.
Trapezoid Area Calculator – Find Area of Any Trapezoid or Irregular Shape
The Trapezoid Area Calculator helps you quickly find the area of any trapezoid (also called a trapezium) — whether regular, isosceles, or irregular.
Just enter the two base lengths and height (or use all four sides if available) to get accurate area results in square inches, feet, centimeters, and meters.
💡 Ideal for geometry, land measurement, construction, and design.
Trapezoid Area Formula (Base, Height, or 4 Sides)
The Trapezoid Area Calculator supports multiple calculation methods depending on what information you have.
When the height is known, use the standard formula:
- Standard formula (height known):
A = ½ × (b₁ + b₂) × h - When height is missing (using sides): apply Bretschneider’s formula or the calculator’s “4-sides” mode.
- For isosceles trapezoids: height can be derived from side length using the Pythagorean theorem.
💡 Tip: Always make sure both base lengths (b₁ and b₂) are the parallel sides — that’s essential for accurate results.
Example Calculations
Here are a few Trapezoid Area Calculator examples showing different input methods and units:
- Example 1: b₁ = 8 in, b₂ = 12 in, h = 6 in → A = ½ × (8 + 12) × 6 = 60 in²
- Example 2: b₁ = 10 cm, b₂ = 14 cm, h = 8 cm → A = ½ × (10 + 14) × 8 = 96 cm²
- Example 3 (Irregular): a = 9 m, b = 12 m, c = 8 m, d = 11 m → A ≈ 89.6 m²
💡 Try these examples in the calculator to see the difference between regular and irregular trapezoids in real time.
Conversion Table – Common Units
| Bases (b₁ + b₂) | Height | Area (in²) | Area (cm²) | Area (ft²) |
|---|---|---|---|---|
| 8 + 12 | 6 | 60 | 387.10 | 0.42 |
| 10 + 20 | 15 | 225 | 1451.6 | 1.56 |
| 5 + 7 | 4 | 24 | 154.8 | 0.17 |
💡 Tip: 1 in² = 6.4516 cm², 1 ft² = 144 in².
Practical Uses
- Geometry & Education: Demonstrate the base-average method and height relation for students learning area concepts.
- Land Surveying: Estimate irregular land plots with non-parallel sides using trapezoidal approximations.
- Construction: Calculate trapezoidal slabs, ramps, road shoulders, and roof cross-sections with high precision.
- Interior Design: Measure angled or slanted furniture surfaces for flooring and custom-fit materials.
💡 Tip: The Trapezoid Area Calculator adapts to both regular and irregular shapes, making it ideal for practical field work and academic use alike.
Common Mistakes
- Confusing bases with non-parallel sides: Only the two parallel sides (b₁ and b₂) are used in the trapezoid area formula — not the slanted or angled sides.
- Using wrong height value: The height (h) must always be the perpendicular distance between the two parallel bases, not the slanted side length.
- Mixing trapezoid with parallelogram formulas: Some users mistakenly apply the parallelogram formula (A = base × height), which doesn’t account for two different base lengths in a trapezoid.
- Combining different measurement units: Entering one base in inches and the other in centimeters leads to large calculation errors — always use consistent units.
- Assuming both non-parallel sides are equal: That’s only true for an isosceles trapezoid. For irregular ones, the sides may vary greatly, affecting height and total area.
💡 Tip: Before calculating, double-check which sides are parallel and ensure your height is measured at a right angle to them — it’s the most common source of error.
FAQs – Trapezoid Area Explained
1. What is the formula for the area of a trapezoid?
The standard formula is A = ½ × (b₁ + b₂) × h, where b₁ and b₂ are the parallel bases and h is the height between them.
2. What is b₁ and b₂ of a trapezoid?
b₁ and b₂ represent the two parallel sides of the trapezoid — their average multiplied by the height gives the total area.
3. How to find area of 4 unequal sides?
Use Bretschneider’s formula or switch to the calculator’s 4-sides mode — it automatically determines the height and area using all side lengths.
4. What are other ways to find trapezoid area?
Besides the height formula, you can use side lengths, diagonals, or trigonometric methods depending on which values are known.
5. How to calculate the area of a trapezoid without height?
When height is unknown, use all four sides or derive height using the Pythagorean theorem if it’s an isosceles trapezoid.
6. What is the perimeter of a trapezoid?
The perimeter = b₁ + b₂ + a + c (the sum of all sides). The calculator can also compute this for you instantly.
7. How is a trapezoid different from a parallelogram?
A trapezoid has only one pair of parallel sides, while a parallelogram has two pairs of parallel sides. Their area formulas differ accordingly.
Conclusion – Understanding Trapezoid Area
The Trapezoid Area Calculator simplifies how you measure four-sided figures — from regular trapezoids to complex land shapes.
By entering the base lengths and height (or all four sides), you get instant, accurate area results in multiple units.
This tool combines geometry precision with real-world practicality — helping students, engineers, and builders calculate areas for slabs, ramps, roofs, and irregular plots without manual formulas.
💡 Key Takeaways:
• Use A = ½ × (b₁ + b₂) × h for regular trapezoids.
• Switch to “4-sides mode” for irregular shapes.
• Keep measurements consistent — don’t mix units.
• Always measure the perpendicular height, not the slanted side.
🔗 Try more tools:
Rectangle Area Calculator,
Triangle Area Calculator,
Circle Area Calculator,
or
Sector Area Calculator
to explore more shapes and conversions.
📘 Read more:
Wikipedia – Area of a Trapezoid