Trapezoid Area Calculator
Area of a trapezoid from its two parallel sides and perpendicular height, with the working shown.
In short
Area of a trapezoid from its two parallel sides and perpendicular height, with the working shown.
Formula: A = (a + b) ÷ 2 × h, where a and b are the parallel sides and h is the perpendicular distance between them.
What this calculator does
Area of a trapezoid from its two parallel sides and perpendicular height, with the working shown. Formula, worked example, sources, FAQs and limitations included.
You enter parallel side a, parallel side b, perpendicular height h and unit (labels only — no conversion), and the trapezoid area calculator shows the answer along with the working, so you can check it or try other numbers.
The page shows the formula, a numeric worked example, and the assumptions that affect this math calculation.
Inputs and what they mean
- Parallel side a
- — number value.
- Parallel side b
- — number value.
- Perpendicular height h
- — number value.
- Unit (labels only — no conversion)
- — choice value.
How to use it
- Enter each value in the unit shown next to the box (use the unit converter first if your numbers are in other units).
- Check the breakdown to see every intermediate step.
- Read the limitations before relying on the result.
Formula
Source: Wolfram MathWorld, Trapezoid.
Height must be perpendicular to the parallel sides, not the slanted leg length.
A = (a + b) ÷ 2 × h, where a and b are the parallel sides and h is the perpendicular distance between them.
Inputs used: Parallel side a, Parallel side b, Perpendicular height h, Unit (labels only — no conversion).
Worked example
Trapezoid 6 and 10 with height 4
- Mean of parallel sides = (6 + 10) ÷ 2 = 8.
- Area = 8 × 4 = 32 cm².
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
- Plane (Euclidean) trapezoids only.
- Does not compute perimeter, because leg lengths are not determined by these inputs.
- Exact mathematical relationships, rounded for display. Check units and rounding before using a result in graded, engineering or financial work.
- The result depends on the values you enter for this trapezoid area calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.
Reference: Wolfram MathWorld
Last reviewed:
Common questions
Can I use the slanted side as height?
No. Use the perpendicular height between the two parallel sides.
Does the order of a and b matter?
No. The formula averages the two parallel sides.
Does changing the unit convert my numbers?
No. The unit only labels the result; enter all lengths in the same unit.
How do I use the Trapezoid Area Calculator?
Enter the required values for Parallel side a, Parallel side b, Perpendicular height h, Unit (labels only — no conversion). The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.
What formula does the Trapezoid Area Calculator use?
A = (a + b) ÷ 2 × h, where a and b are the parallel sides and h is the perpendicular distance between them. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.
Can the Trapezoid Area Calculator be used for exact decisions?
Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.
Sources
Method based on Wolfram MathWorld.
Cite this page
Free Calculator. (2026, November 3). Trapezoid Area Calculator. https://freecalculator.tech/tools/trapezoid-area-calculator
"Trapezoid Area Calculator." Free Calculator, 3 Nov. 2026, https://freecalculator.tech/tools/trapezoid-area-calculator.
Trapezoid Area Calculator — Free Calculator, https://freecalculator.tech/tools/trapezoid-area-calculator
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