# Area and Perimeter

# Donut - Metric

Calculate the area and perimeter of a donut shape.

This calculator uses metres for measurements.

Donut = a circle with a smaller circle centred inside

### Donut Area and Perimeter - Metric

#### Calculation

- outer diameter in metres
- inner diameter in metres
- decimal precision, the number of digits after the decimal point

#### Results

- the inner area in square metres
- total area (donut area plus inner area) in square metres
- the area of the donut in square metres
- the area in square feet
- the area in square inches
- the outer perimeter of the donut in metres
- the outer perimeter in feet
- the outer perimeter in inches
- the inner perimeter of the donut in metres
- the inner perimeter in feet
- the inner perimeter in inches

##### Formula

A = ta-ti
ta = 𝛑D²
ti = 𝛑d²
𝛑 = 3.14159265
PO = 𝛑D
PI = 𝛑d
PO the outer perimeter of the donut
PI the inner perimeter of the donut

##### Conversions

one metre (m) = 3.28083989501312 feet (ft)
one metre (m) = 39.3700787401575 inches (in)
one square metre (m²) = 10.7639104167097 square feet (ft²)
one square metre (m²) = 1550.0031000062 square inches (in²)

### Area and Perimeter of Various Shapes

### Changing the shape of an Area

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