## Let’s get started!

Remember, the input can only be in feet (ft), inches (in), yards (yd), centimetres (cm), millimetres (mm) and metres (m) but never a combination of two different units!

Outer diameter = Inner diameter + (2 x Border width)

Outer area = π x (Outer diameter/2)^2

Inner Area = π x (Inner diameter/2)^2

Area of a Circle Border = Outer area – Inner area

π = 3.142

Inner diameter (drop down ft, in, yd, cm, mm, m)

Border width (drop down ft, in, yd, cm, mm, m)

Price per unit (drop down ft^{2}, in^{2}, yd^{2}, cm^{2}, mm^{2}, m^{2})

# Understanding the Square footage:

To understand how to calculate square footage we must first begin with the definition of area. An area is the size of a two-dimensional surface. The area of a circle is the space contained within its circumference (outer perimeter). To find out the area of a circle border, we need to know its inner diameter and the width of the circular border. The diameter and border width should be measured in feet (ft) for square footage calculations and if needed, converted to inches (in), yards (yd), centimetres (cm), millimetres (mm) and metres (m).

**The formula:**

Outer diameter = Inner diameter + (2 x Border width)

Outer area = π x (Outer diameter/2)^2

Inner area = π x (Inner diameter/2)^2

Area of a Circle Border = Outer area – Inner area

π = 3.142

**Answer** = (Outer area – Inner area) square area

**Abbreviations of unit area: ** ft^{2}, in^{2}, yd^{2}, cm^{2}, mm^{2}, m^{2}

**Where do you need it in daily life?**

Our Square Footage Calculator helps you calculate the area required for making circular wall mouldings and landscaping designs, carpeting, wall decals, centre moulding on a ceiling and floor tiling.

**What measurements do you need?**

You need to know the inner diameter of the circle and the border width in either feet (ft), inches (in), yards (yd), centimetres (cm), millimetres (mm) or metres (m).

**What can you calculate with this tool?**

You can calculate the area of the circle border in square feet, in square inches, square yards, square centimetres, square millimetres and square meters. Yes, our tool is that awesome.

Our calculator gives you the option of calculating the exact cost of materials. All you have to do is enter the price per unit area and voila, you have the total cost of materials in a single click!

**Conversion factors:**

To convert among square feet, square inches, square yards, square centimetres, square millimetres and square meters you can utilize the following conversion table.

Square feet to square yards | multiply ft^{2} by 0.11111 to get yd^{2} |

Square feet to square meters | multiply ft^{2} by 0.092903 to get m^{2} |

Square yards to square feet | multiply yd^{2} by 9 to get ft^{2} |

Square yards to square meters | multiply yd^{2} by 0.836127 to get m^{2} |

Square meters to square feet | multiply m^{2} by 10.7639 to get ft^{2} |

Square meters to square yards | multiply m^{2} by 1.19599 to get yd^{2} |

Square meters to square millimetres | multiply the m^{2} value by 1000000 to get mm^{2} |

Square meters to square centimetres | multiply the m^{2} value by 10 000 to get cm^{2} |

Square centimetres to square metres | multiply the cm^{2} value by 0.0001 to get mm^{2} |

Square centimetres to square millimetres | multiply the cm^{2} value by 100 to get mm^{2} |

Square millimetres to square centimetres | multiply the mm^{2} value by 0.000001 to get cm^{2} |

Square millimetres to square metres | multiply the mm^{2} value by 1000000 to get m^{2} |