Right Triangle Calculator – Find Sides and Angles
Solve a right triangle: sides, angles, area and perimeter from any two sides.
About the Right Triangle Calculator
What is the Right Triangle Calculator?
A right triangle calculator solves the entire triangle — remaining side, angles, area and perimeter — from any two sides.
Why use this calculator?
Rooflines, ramps and trigonometry homework repeatedly call for the same two facts: Pythagoras and sine definitions.
How to use it
- Enter any two of the three sides; set the third to 0.
- Read the missing side, the acute angles, area and perimeter.
Formula
c² = a² + b²; sin(angle) = opposite ÷ hypotenuse.
Angles are reported in degrees.
Frequently Asked Questions
What if I only know one side?
One side is not enough — you need any two sides, or a side and one acute angle.
Are angles always acute?
In a right triangle the two non-90° angles sum to 90°, so yes, both are acute.
What order of operations does this use?
It follows standard PEMDAS/BODMAS rules: parentheses, exponents, multiplication and division, then addition and subtraction.
How precise are the answers?
The calculator uses double-precision floating-point math (about 15 significant digits) and rounds the display. For exact symbolic results use dedicated algebra software.
Can I enter negative numbers or decimals?
Yes. Negative values, decimals and very large or small numbers are all supported unless a field says otherwise.
What does it mean if I get an error?
Errors usually mean an invalid input, such as division by zero or a negative value where only positives make sense. Check your entries and try again.
Which units should I use?
Use one consistent unit for every input. The result will be in that unit (or its square or cube for area and volume).
How is area different from perimeter?
Perimeter is the distance around a shape; area is the space it covers. Perimeter is measured in units, area in square units.
Does the orientation of the shape matter?
No. Area, perimeter and volume depend only on the dimensions, not on how the shape is rotated or positioned.
Is this calculator free to use?
Yes. Every calculator on this site is completely free, with no hidden fees, no subscriptions and no limits on how many times you can use it.