Math & Statistics · Browser · Free

Right Triangle Calculator

Enter two sides, or one side and an angle, then press Calculate to see the sides, angles and area of the right triangle. Choosing Trigonometric functions calculator evaluates trig functions.

What this tool does

The right triangle calculator finishes a right triangle from values you supply. Enter two sides, such as Side a: 3 and Side b: 4, or one side and an angle, such as Side a: 3 and Angle A: 30, then press Calculate. Results appear in cards below the button and list Side a, Side b, Side c, Angle A, Angle B and Area. For Side a: 3 and Side b: 4 the cards read Side c: 5, Angle A: 36.869897645844 °, Angle B: 53.130102354156 ° and Area: 6.

The Angle unit select chooses between Degrees (°) and Radians (rad). Copy writes a result and its unit to the clipboard. Clear resets the form. Everything runs in the browser and nothing is uploaded.

In the Mode select, choosing Trigonometric functions calculator lets you pick a Trig function (sin, cos, tan, csc, sec, cot, arcsin, arccos, arctan, arccsc, arcsec, arccot) and enter a number in Input x.

Right triangle and trig formulas

The sides a and b meet at the right angle, and c is the hypotenuse, the side opposite it. The worked examples show the relations at work: c = √(a² + b²), so c = √(3² + 4²) = 5 when a = 3 and b = 4; and b = √(c² - a²), so b = √(5² - 3²) = 4 when a = 3 and c = 5. With a = 1 and b = 1 the third side comes out as c = √(1² + 1²) ≈ 1.4142135623731, and Angle A is 45 °.

Angle A sits opposite side a. Given Side a: 3 and Angle A: 30, the tool reports b = a / tan(A) = 3 / tan(30) ≈ 5.19615242270663, Side c: 6, Angle B: 60 ° and Area: 7.79422863405995.

In the trigonometric mode the function works on the number in Input x. With Degrees (°) as the angle unit, sin(30) = 0.5, which is the Result: 0.5 the calculator shows for Input x: 30.