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Geometry

Triangle Side Length Checker

Check whether three lengths form a triangle and classify its angle type.

Use consistent dimensionsArea and volume units explained below
Geometry desk
Geometry desk

Match each dimension to the shape and keep units consistent.

See the method

Set the dimensions

Runs on your device

Your measurement

Your result

Let’s calculate.

Use the Calculate button to see your result.

Review the method below for assumptions and conventions.

How to use this tool

  1. Enter first length, second length, third length.
  2. Select Calculate to view the result.
  3. Check the method and assumptions below before using the result.

The method, explained

Sort x≤y≤z. A triangle requires x+y>z. Compare x²+y² with z² to classify acute, right or obtuse.

A WORKED EXAMPLE

Using first length = 3 units, second length = 4 units, third length = 5 units, the result is Right triangle (within tolerance). Change these example inputs to match your task; use the method above to check each step.

Understanding your result

The right-angle test uses a numerical tolerance. It is a length consistency check, not a measurement accuracy assessment.

What to keep in mind

The right-angle test uses a numerical tolerance. It is a length consistency check, not a measurement accuracy assessment. Use the indicated units consistently. Ideal shapes are assumed; dimensions must describe the same object. Display rounding does not increase measurement precision.

Common questions

How do I use this triangle side length checker?

Check whether three lengths form a triangle and classify its angle type. Enter first length in units, second length in units, third length in units. The starting example is editable; use values for the same system or project.

Which assumptions affect this result?

The right-angle test uses a numerical tolerance. It is a length consistency check, not a measurement accuracy assessment.

Methodology maintained by ClarityKit. How these tools are built and checked.