Formulas, without the guesswork.
Choose a relationship from the measurements you know. The variable names below belong to each calculator; a letter can have a different role in another method. π is evaluated using the browser’s full numerical constant, rather than replacing it with 3.14.
Two perpendicular legs
Inputs: Leg a (length units); Leg b (length units).
Hypotenuse and one leg
Inputs: Hypotenuse c (length units); Leg a (length units).
Adjacent leg and acute angle
Inputs: Adjacent leg b (length units); Acute angle θ (degrees).
Hypotenuse and acute angle
Inputs: Hypotenuse c (length units); Acute angle θ (degrees).
Reading the notation
√ means a square root, ∛ means a cube root, and a superscript ² or ³ means a square or cube. Sine, cosine and tangent use angles converted from entered degrees. Where an inverse trigonometric function is used, its displayed angle is converted back to degrees. The ellipse perimeter is approximate; other formula labels describe the ideal mathematical model.
The hypotenuse must exceed either leg. Acute-angle calculators require an angle strictly between 0 and 90 degrees.
Reference reading: Right triangle at Wolfram MathWorld.