The semi-perimeter of a triangle calculator 
Triangle computes half the length of the perimeter of a triangle.
INSTRUCTIONS: Choose units and enter the following:
- (a) - length of side a
- (b) - length of side b
- (c) - length of side c
Semi-Perimeter (s): The calculator computes the semi-perimeter in meters. However, this can be automatically converted to many other length units (e.g. inches) via the pull-down menu.
This formula also confirms that the three length can form a triangle. If not, an error message is returned.
The Math/Science
The formula for the semi-perimeter of a triangle is:
s = (a + b + c) / 2
where:
- s = semi-perimeter of triangle
- a, b, c = length of the three sides of the triangle.
A triangle is a polygon with three sides, three vertices (corners), and three angles. 
Triangles can be classified based on the lengths of their sides and the measures of their angles as follows:
By Side Lengths:
- Equilateral Triangle: All three sides are equal in length.
- Isosceles Triangle: Two sides are equal in length.
- Scalene Triangle: All three sides have different lengths.
By Angle Measures:
- Acute Triangle: All three angles are less than 90 degrees.
- Right Triangle: One angle is exactly 90 degrees.
- Obtuse Triangle: One angle is greater than 90 degrees.
The sum of the interior angles of any triangle always adds up to 180 degrees.
Triangle Calculators
- Area of Triangle (base and height)
- Area of Triangle (two sides and interior angle)
- Area of Triangle (two angles and interior side)
- Area of Triangle (three sides)
- Area of Equilateral Triangle
- Area of Triangle (three points)
- Height of Triangle
- Width of Triangle
- Triangle Perimeter
- Interior Angle of a triangle based on the length of three sides
- Semi-perimeter of a triangle
- Area of Circle Within a Triangle
- Area of Circle Around a Triangle
- Area between two vectors
- Triangle Volume
References
- Light and Matter(Dr. Benjamin Crowell) Chapter 0.12 Summary