Triangle Perimeter Calculator
Calculate triangle perimeter from three sides, one equilateral side, equal side and base, or two right-triangle legs with triangle inequality checks.
Triangle perimeter from known sides
The dominant English intent is direct: add the side lengths and validate whether the triangle can exist. The calculator also covers common classroom variants such as equilateral, isosceles, and right triangles.
| Mode | Inputs | Validation |
|---|---|---|
| Three sides | Side a, side b, side c | Triangle inequality |
| Equilateral | One side | Positive length |
| Isosceles | Equal side and base | Equal sides must be longer than the base when added |
| Right triangle | Two legs | Positive lengths; hypotenuse is computed |
Triangle formulas
P is perimeter; a, b, and c are side lengths.
P is equilateral triangle perimeter; a is side length.
P is isosceles triangle perimeter; a is equal side; b is base.
c is hypotenuse; a and b are right-triangle legs.
Frequently Asked Questions
Sources and References
Calculations are based on the listed reference sources. Links open in a new tab.
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