PERIMETER & CIRCUMFERENCE CALCULATOR
Rectangle, square, triangle, circle, parallelogram and trapezium perimeter formulas
Enter side lengths or radius and get clear GCSE-style working on screen
SHAPE
RECT
Choose the shape first
ROUNDING
2DP
Result rounding only
LENGTH
A
Enter a number
WIDTH
B
Enter a number
WORKING
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PERIMETER
READY
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PAGE SUMMARY
Use this calculator to work out perimeter or circumference for common 2D shapes.
Good for rectangle, square, triangle, circle, parallelogram and trapezium questions.
Useful for school maths, GCSE revision, homework checks and formula practice.
Circle uses circumference, which is the perimeter of a circle.
See formulas, examples and extra perimeter help on the next pages.
Related maths pages are linked below for area, index and more Teletext-Tools pages.
HOW TO USE
Choose a shape, enter the lengths shown and press SOLVE.
Only the measurements needed for that shape are shown.
Circle uses radius and returns circumference.
RECTANGLE / SQUARE
Rectangle: P = 2(L + W)
Square: P = 4s
Example: 2(8 + 5) = 26
TRIANGLE
P = a + b + c
Add all three sides.
Example: 3 + 4 + 5 = 12
CIRCLE
C = 2πr
π ≈ 3.14159
Example: r = 4 gives 25.13
PARALLELOGRAM
P = 2(a + b)
Add a pair of adjacent sides, then double.
TRAPEZIUM
P = a + b + c + d
Add all four sides.
Use measured side lengths if needed.
PAGE 2/4
PERIMETER CALCULATOR FOR SHAPES
This page helps you calculate the perimeter of common 2D shapes quickly.
It suits learners checking formulas for rectangles, squares, triangles and trapeziums.
It is also useful for school maths and GCSE perimeter questions.
CIRCUMFERENCE HELP
The perimeter of a circle is called the circumference.
This page uses the radius and applies the formula C = 2πr.
COMMON SEARCHES
perimeter calculator for shapes
circumference calculator with working
triangle perimeter calculator
GCSE perimeter formulas
UNITS
Perimeter uses the same units as the side lengths.
If lengths are in cm, the perimeter is in cm.
Unlike area, perimeter is not squared.
PAGE 3/4
WORKED EXAMPLES
Rectangle: 2(12 + 4) = 32
Square: 4 × 6 = 24
Triangle: 7 + 8 + 9 = 24
Circle: 2π × 3 ≈ 18.85
WHY THIS PAGE HELPS
It gives a quick answer and a clear method.
It helps users compare different perimeter formulas in one place.
It also supports the move from shape basics into area and more advanced geometry pages.
RELATED TELETEXT-TOOLS PAGES
LOOP BACK
Use NEXT to return to Page 1 and keep calculating.
This keeps the calculator clear on the first page while still giving strong extra help.
PAGE 4/4
SHAPE
RECT
Choose the shape first
ROUNDING
2DP
Result rounding only
LENGTH
A
Enter a number
WIDTH
B
Enter a number
WORKING
—
—
—
—
—
PERIMETER
READY
—
PAGE 1/4
HOW TO USE
Choose a shape, enter the lengths shown and press SOLVE.
Circle returns circumference.
RECTANGLE / SQUARE
Rectangle: P = 2(L + W)
Square: P = 4s
TRIANGLE
P = a + b + c
CIRCLE
C = 2πr
Use the radius.
PARALLELOGRAM / TRAPEZIUM
Add all outside sides
Para: P = 2(a + b)
EXAMPLES
2(8 + 5) = 26
4 × 6 = 24
2π × 4 ≈ 25.13
PAGE 2/4
PERIMETER OF SHAPES
This page helps calculate the perimeter of common 2D shapes.
It is useful for rectangle, square, triangle and trapezium questions.
CIRCUMFERENCE
The perimeter of a circle is called the circumference.
This page uses C = 2πr.
COMMON SEARCHES
perimeter calculator for shapes
circumference calculator with working
triangle perimeter calculator
GCSE perimeter formulas
UNITS
Perimeter uses the same unit as the side lengths.
Perimeter is not squared.
PAGE 3/4
WHY THIS PAGE IS USEFUL
It keeps the calculator clear on Page 1 and moves the extra guide content here.
This makes the tool easier to use on desktop, laptop, tablet and phone screens.
WORKED VALUES
Rectangle: 2(12 + 4) = 32
Triangle: 7 + 8 + 9 = 24
Circle: 2π × 3 ≈ 18.85
RELATED PAGES
LOOP BACK
Use NEXT to return to Page 1 and continue calculating.
PAGE 4/4