Perimeter Formulas — All Shapes Reference A complete reference of perimeter formulas. Perimeter is the distance around a closed 2D figure. For circles the perimeter is called the circumference. Each formula links to its full page where available.
Triangles General Triangle
P = a + b + c P = a + b + c P = a + b + c Right Triangle (legs a, b)
P = a + b + a 2 + b 2 P = a + b + \sqrt{a^2 + b^2} P = a + b + a 2 + b 2 Quadrilaterals Rectangle
P = 2 ( l + w ) P = 2(l + w) P = 2 ( l + w ) Parallelogram
P = 2 ( a + b ) P = 2(a + b) P = 2 ( a + b ) Trapezoid
P = a + b + c + d P = a + b + c + d P = a + b + c + d Kite (sides a, b)
P = 2 a + 2 b P = 2 a + 2 b P = 2 a + 2 b Regular Polygons Regular Polygon (n sides, length s)
Circle (Circumference) Arc Length (degrees)
s = θ 360 ° ⋅ 2 π r s = \frac{\theta}{360°} \cdot 2 \pi r s = 360° θ ⋅ 2 π r Curves (Calculus) L = ∫ a b 1 + ( d y d x ) 2 d x L = \int_a^b \sqrt{1 + \left(\frac{dy}{dx}\right)^2}\,dx L = ∫ a b 1 + ( d x d y ) 2 d x Arc Length (Parametric)
L = ∫ a b ( x ′ ( t ) ) 2 + ( y ′ ( t ) ) 2 d t L = \int_a^b \sqrt{(x'(t))^2 + (y'(t))^2}\,dt L = ∫ a b ( x ′ ( t ) ) 2 + ( y ′ ( t ) ) 2 d t Arc Length (Polar)
L = ∫ α β r 2 + ( d r d θ ) 2 d θ L = \int_\alpha^\beta \sqrt{r^2 + \left(\frac{dr}{d\theta}\right)^2}\,d\theta L = ∫ α β r 2 + ( d θ d r ) 2 d θ 