Trapezoid Angle Calculator

Trapezoid Angles Explained

A trapezoid has four interior angles: $\alpha$, $\beta$, $\gamma$, and $\delta$. Like all quadrilaterals, they sum to $360°$. Because a trapezoid has one pair of parallel sides, angles along each leg are supplementary: $\alpha + \beta = 180°$ and $\gamma + \delta = 180°$.

See also: Supplementary Angles Calculator, Trapezoid Calculator, and Right Trapezoid Calculator.

Angle Rules

Supplementary pairs:

$$\alpha + \beta = 180° \quad \gamma + \delta = 180°$$

Full quadrilateral sum:

$$\alpha + \beta + \gamma + \delta = 360°$$

Knowing any one angle in a pair gives the other. Knowing three angles determines the fourth.

Worked Example

If $\alpha = 75°$ and $\delta = 95°$, then $\beta = 105°$ and $\gamma = 85°$. Check: $75 + 105 + 85 + 95 = 360°$.