How it works
The formula averages the parallel sides and multiplies by height — equivalent to splitting into a rectangle and two triangles.
Formula
A = ½ × (b₁ + b₂) × h
How to use Area of a Trapezoid Calculator
- Enter parallel base lengths b₁ and b₂.
- Enter the height (altitude), not the slant leg.
- Calculate area in square units.
- Pair with rectangle area for floor plans mixing shapes.
Worked examples
Concrete numbers and cases you can check against the tool above.
Bases 20 ft and 28 ft, height 15 ft
A = ½×(20+28)×15 = 360 ft².
When to use Area of a Trapezoid Calculator
Trapezoids model roof ends, tabletops with tapered edges, and composite shapes split from irregular plots.
Common use cases
- Land area between parallel road and river edges approximated as trapezoid.
- Cross-section area in civil engineering sketches.
- Homework on quadrilateral area formulas.
Inputs and outputs
- Two bases and height in consistent units
Privacy
This tool runs entirely in your browser. Your data never leaves your device — nothing is uploaded to our servers.
Frequently asked questions
- Is height the same as a side length?
- No — height is perpendicular distance between the parallel bases unless the trapezoid is right.
- What if bases are equal?
- You get a parallelogram; area reduces to base × height.
- Can bases be in different units?
- Convert to one unit first or the area will be wrong.