Calculate the perimeter of a triangle from its three side lengths with semi-perimeter and individual side breakdown.
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Result
Perimeter
Semi-perimeter
6
Area
6
Type
Scalene
Also in Triangles
Triangle Geometry
The triangle perimeter calculator sums the three side lengths of a triangle and shows the semi-perimeter. It also checks whether the three lengths satisfy the triangle inequality before computing results.
The perimeter is the total length of the boundary. The semi-perimeter is half the perimeter and is used in many triangle formulas, including Heron's formula for area and the inradius formula.
P = a + b + c
The perimeter is the sum of all three sides.
s = P / 2
The semi-perimeter is half the perimeter.
Three positive lengths form a valid triangle only when every pair sums to more than the third side. This calculator validates that condition before reporting the perimeter, ensuring the input represents a real triangle.
Perimeter is essential for fencing triangular plots, framing triangular structures, or estimating material for trim and edging around triangular shapes.
Frequently asked questions
It appears in Heron's formula for area, the inradius formula r = Area / s, and many other triangle identities.
Yes. Many different triangles can share the same perimeter but have different shapes, areas, and angles.
Related
These related calculators come from the same leaf category, nearby sibling categories, or the same top-level topic.
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