Geometry Formulas
A quick reference to the core formulas used across the calculators on areacalculator.io.
Area formulas
- Circle:
A = πr² - Square:
A = s² - Rectangle:
A = w × h - Triangle:
A = 1/2 × b × h - Trapezoid:
A = 1/2 × (a + b) × h - Ellipse:
A = πab - Parallelogram:
A = b × h - Sector:
A = 1/2 × r² × θ, with θ in radians
Use the Area Calculator to calculate these values directly.
Surface area formulas
- Cube:
SA = 6s² - Rectangular prism:
SA = 2(lw + lh + wh) - Sphere:
SA = 4πr² - Cylinder:
SA = 2πr(r + h) - Cone:
SA = πr(r + l)
Use the Surface Area Calculator for shape-specific inputs.
Volume formulas
- Cube:
V = s³ - Rectangular prism:
V = l × w × h - Sphere:
V = 4/3 × πr³ - Cylinder:
V = πr²h - Cone:
V = 1/3 × πr²h - Pyramid:
V = 1/3 × base area × h
Use the Volume Calculator for instant results.
Input rule
Use one measurement unit at a time. For example, do not mix centimeters and meters in the same calculation unless you convert them first.
How to read geometry formulas
A formula is a compact way to describe a measurement relationship. In area formulas, the answer is in square units. In volume formulas, the answer is in cubic units. Symbols such as r, h, w, and l stand for radius, height, width, and length.
Common symbols
- r: radius, usually used for circles, spheres, cylinders, and cones.
- h: height, often a perpendicular measurement.
- w: width.
- l: length.
- π: pi, approximately 3.14159265358979.
Formula examples
Circle area: A = πr²
Rectangle area: A = w × h
Cylinder volume: V = πr²h
Sphere surface area: SA = 4πr²