Right Triangle Calculator

What is the Right Triangle Calculator?

Solve a right triangle from one leg and an acute angle. Knowing one side and one angle of a right triangle is enough to find every other side and angle with trigonometry.

How to use the Right Triangle Calculator

1. Enter your adjacent leg, your angle θ.
2. Results update automatically as you type; you can also press Calculate.
3. Read the output: opposite leg, hypotenuse, area.
4. Use the 📊 chart to see the result visually, then copy or share it.

Formula and method

Worked example

With adjacent leg = 10, angle θ = 30 °, the Right Triangle Calculator returns opposite leg: 5.7735026919; hypotenuse: 11.5470053838; area: 28.8675134595.

Where the Right Triangle Calculator helps in real life

A roofer knows a roof rises at 30° and the horizontal run is 4 meters. The calculator gives the rafter length and the rise.

A wheelchair ramp must rise 0.6 meters at a gentle angle. Solving the triangle shows how long the ramp must be.

Common mistakes to avoid

• Entering the angle in radians when the tool expects degrees.
• Using the right angle as the known acute angle.
• Mixing up the opposite and adjacent sides.
• Rounding intermediate results before finding the last side.

💡 Practical tip: Sine, cosine and tangent are just the ratios between pairs of sides for a given angle.

Tips for better results

• Label the hypotenuse, opposite and adjacent sides on a sketch.
• Check the result with the Pythagorean theorem.
• Keep the angle under 90° — it must be acute.

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