Trapezoid area calculator

Calculate trapezoid area from two parallel bases and perpendicular height. Apply A = (B + b) × h ÷ 2 and compare the result with a worked example.

Result

Why use the mean base?

The mean base accounts for the trapezoid narrowing. Equal bases reduce the formula to the rectangle’s area formula.

How do you calculate trapezoid area?

Add the parallel bases, divide by two, then multiply by perpendicular height. The mean base is the length of the parallel segment halfway up the shape.

A = \frac{(B + b) \times h}{2}

h = \frac{2 \times A}{B + b}

How to use the calculator

Enter measurements with a decimal point or comma: results update immediately. Input units apply to every length; changing them converts the measurements. Changing result units leaves the shape unchanged. The control below the drawing reveals or hides its visual explanation. Copy results includes valid measurements and the result. Reset and Try this example restore the initial values and centimetre units.

Choose Bases and height to find area, or Bases and area to find height. Entered area uses square units. In inverse mode at least one base must be positive; moving the handles updates area while keeping the other dimensions.

The first formula shows the relationship; the second substitutes measurements converted to the result unit. The ≈ sign indicates rounding, including in the substituted values.

A trapezoidal panel

A panel has parallel bases of 8 and 4 cm separated by 3 cm. Their mean is 6 cm, so multiplying by height gives an area of 18 cm².

From measurements to the result

Input: $B = 8 cm; b = 4 cm; h = 3 cm$
Result: $18 {cm}^{2}$

Calculation steps

Find the mean of the two parallel bases.
$m = \frac{8 + 4}{2} = 6$
Complete the calculation using the tool’s formula.
$A = 6 \times 3 = 18$

Units and interpretation

Area uses square units: 1 m² = 10,000 cm².

Enter the bases in either order. Perimeter cannot be determined without the sloping sides.

Precision and numerical limits

Lengths range from 0 to 10¹² in the selected unit; triangle sides must be strictly positive. Results use two decimal places, with scientific notation for very small or large values. Calculations use browser precision: unrepresentable positive values produce an error. A rejected unit change keeps the previous data. Calculation takes place in your browser.

Entered area may reach 10²⁴, provided the derived height is at most 10¹² in the input unit. A rejected mode change keeps the previous data.

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Trapezoid area calculator

Result

Why use the mean base?

How do you calculate trapezoid area?

How to use the calculator

A trapezoidal panel

From measurements to the result

Calculation steps

Units and interpretation

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Circle area

Circle circumference

Triangle area