CalmCalc
MATH

Right Triangle Calculator

Estimate side b from side a, side b, hypotenuse c with the Right Triangle Calculator.

Choose the known measurementsSolve a right triangle from two independent measurements.
5 options
SIDE B12 m

All sides, acute angles, area, and perimeter are reported below.

a
5
b
12
c = h
13
Area (A)
30
Perimeter (P)
30
Angle α
22.61986495°
Angle β
67.38013505°
Estimate based on the values shown
MethodSolves all sides, acute angles, area, and perimeter from legs, a hypotenuse and leg, or either supported side-and-angle pairing.

Before you use the result

The result depends on the entered values, selected mode, and displayed mathematical assumptions.

CALCULATOR GUIDE

How to use the Right Triangle Calculator

Estimate side b from side a, side b, hypotenuse c with the Right Triangle Calculator. It includes Two legs, Hypotenuse and one leg, Leg a and angle α, Hypotenuse and angle α, Leg b and angle β workflows, so choose the one that matches the values you actually know. Use it to check the arithmetic while keeping the displayed method and entered values with your work.

Step by step

  1. For the Right Triangle, enter side a, side b, hypotenuse c, angle α, angle β. Keep each value in the unit displayed beside its field.
  2. Review the selected Right Triangle workflow and inputs, then read side b in the result panel.
  3. Change one Right Triangle assumption at a time to compare scenarios. Use Reset to restore this tool's worked example values.

How the calculation works

Solves all sides, acute angles, area, and perimeter from legs, a hypotenuse and leg, or either supported side-and-angle pairing.

Worked example

In the Right Triangle worked example, side a 5, side b 12, hypotenuse c 13, angle α 30 degree produces side b of 12. All sides, acute angles, area, and perimeter are reported below. Review the displayed units before comparing the result.

Understanding the result

The Right Triangle reports side b. Use it to check the arithmetic while keeping the displayed method and entered values with your work. The result depends on the entered values, selected mode, and displayed mathematical assumptions.

How to check the answer

Check the Right Triangle answer by substituting side b back into the stated relationship. Test a simple value such as zero, one, or an equal pair, then confirm that sign, scale, units, and rounding match Solves all sides, acute angles, area, and perimeter from legs, a hypotenuse and leg, or either supported side-and-angle pairing.

Common questions

What does the Right Triangle calculate?

Estimate side b from side a, side b, hypotenuse c with the Right Triangle Calculator.

Which Right Triangle inputs have the biggest effect?

side b responds directly to side a, side b, hypotenuse c, angle α, angle β. Change one input while holding the others constant to see its effect.

Is the Right Triangle result exact?

The result depends on the entered values, selected mode, and displayed mathematical assumptions. Recheck side a, side b, hypotenuse c and use side b only for a decision where that level of precision is appropriate.

Formula tests, limits, sources, and guide registry updated September 1, 2026.
INTERPRET THE RESULTRead the math guideCheck assumptions, limitations and comparison methods →