Enter any three side lengths for instant validation. Check inequalities, classify shape, and compute measures. Download results easily and inspect example values before solving.
| Side A | Side B | Side C | Can Form Triangle? | Type |
|---|---|---|---|---|
| 3 | 4 | 5 | Yes | Scalene Right |
| 5 | 5 | 5 | Yes | Equilateral Acute |
| 4 | 4 | 6 | Yes | Isosceles Obtuse |
| 2 | 3 | 6 | No | Invalid |
| 1 | 2 | 3 | No | Degenerate |
The calculator first applies the triangle inequality rule. Three lengths form a triangle only when each pair sum is greater than the remaining side.
If the triangle is valid, perimeter is a + b + c. Semiperimeter is s = (a + b + c) / 2. Area uses Heron's formula: √(s(s-a)(s-b)(s-c)). Angle type is found by comparing the two smaller squared sides with the largest squared side.
This calculator helps you test whether three lengths can make a real triangle. It goes beyond a simple yes or no answer by also reporting classification details, perimeter, semiperimeter, area, inequality margins, and a graph. That makes it useful for homework, exam review, construction checks, drafting tasks, and quick geometry verification.
When the side lengths are valid, the tool identifies whether the triangle is equilateral, isosceles, or scalene. It also checks the angle family by comparing squared side lengths, so you can quickly see whether the result is acute, right, or obtuse. The step section shows the actual inequalities used, which makes the logic easy to follow.
If the lengths fail, the calculator explains why. This is helpful when one side is too long or when the values create a degenerate case. The optional unit field keeps reports readable, and the download buttons let you export results for notes, records, or class material.
Use the triangle inequality rule. Each pair of sides must add to more than the third side. If even one check fails, the lengths cannot form a true triangle.
No. A triangle needs three positive lengths. Zero or negative values do not describe real sides, so the shape is invalid from the start.
A degenerate case appears when two sides add exactly to the third. The points fall on one straight line, so the figure has no real interior area.
Those values are useful after validity is confirmed. Perimeter gives total boundary length, and area shows the enclosed region using Heron's formula.
It sorts the sides, squares them, then compares the two smaller squared values with the largest squared value. Equality indicates a right triangle.
Yes. The tool accepts decimal inputs, so it works for measured values, scaled drawings, engineering estimates, and classroom examples.
For valid data, the graph draws the triangle shape. For invalid data, it charts inequality margins so you can see which condition failed and by how much.
Use downloads when you want to save values, share a report, attach results to notes, or keep a record for study and comparison.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.