Trapezoid Area Calculator Without Base

This trapezoid area calculator solves for the missing base when you know the other base, height, and area. It's perfect for geometry problems where one dimension is unknown.

How to Use This Calculator

To calculate the area of a trapezoid when you don't know one base:

Enter the known base length (b1)
Enter the height (h)
Enter the area (A)
Click "Calculate"
The calculator will solve for the missing base (b2)

The result will show both the missing base and the complete trapezoid area calculation.

Formula Explained

Trapezoid Area Formula

The area of a trapezoid is calculated using the formula:

A = (b1 + b2) × h / 2

Where:

A = Area
b1 = Known base length
b2 = Missing base length (what we're solving for)
h = Height

Solving for the Missing Base

To find the missing base (b2), we rearrange the formula:

b2 = (2 × A / h) - b1

Worked Example

Let's solve for the missing base in a trapezoid with:

Known base (b1) = 8 units
Height (h) = 5 units
Area (A) = 35 square units

Using the formula:

b2 = (2 × 35 / 5) - 8 = (70 / 5) - 8 = 14 - 8 = 6 units

The missing base is 6 units, and the complete trapezoid area is 35 square units.

Frequently Asked Questions

What is a trapezoid?

A trapezoid is a quadrilateral with at least one pair of parallel sides. The parallel sides are called the bases, and the other two sides are the legs.

When would I need this calculator?

This calculator is useful when you know the area, one base, and height of a trapezoid but need to find the missing base length.

Can I use this for irregular quadrilaterals?

No, this calculator is specifically for trapezoids with exactly one pair of parallel sides. For irregular quadrilaterals, you would need a different approach.