Perimeter Calculator
Calculate the perimeter of common shapes: rectangle, triangle, square, regular polygon, and trapezoid. Find the total distance around any polygon from side lengths.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Perimeter Calculator | — | P = sum of all sides | linear units |
Step-by-Step Examples
l=8, w=5.
- P=2(8+5)=2×13=26
a=3, b=4, c=5 (right triangle).
- P=3+4+5=12
- Verify right triangle: 3²+4²=5² ✓
n=6, side=4.
- P=6×4=24
- Interior angles each 120°
Real-World Applications
Common Mistakes to Avoid
Perimeter is the boundary length (1D). Area is the enclosed space (2D). A large perimeter does not mean large area.
C = 2πr or πd. It is not called perimeter for circles — use circumference.
For non-regular shapes, you must sum ALL sides. There is no shortcut unless the shape has symmetry.
Frequently Asked Questions
Related Math Calculators
Formula Explorer connections
Interpretation: This relationship connects dimensions, coordinates, angles or trigonometric ratios to a geometric measurement. Assumption: Use a consistent angle mode and length unit, identify the intended shape or coordinate system, and verify that the supplied dimensions form valid geometry.