Rectangle Perimeter

Also known as perimeter of a rectangle · baseboard length · 2(l+w)

P = 2(l + w)

Worked example: 8 m x 5 m → perimeter 26 m — press Try an example to run it live, then adjust anything.

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Rectangle Perimeter explained

Two lengths and two widths make the trip around, so $P = 2(l + w)$ . It is the baseboard formula, the fence formula, the picture-frame formula: a 4 m × 3 m room needs 14 m of trim, minus the doorways. Solving backwards is just as common — with 30 ft of edging and a 10 ft side already fixed, the other side must be 5 ft.

The contrast with area is worth holding onto. Perimeter grows in step with size while area grows with its square, so of all rectangles with a 20 m perimeter, the 5 × 5 square encloses 25 m² while a long thin 9 × 1 encloses only 9 m². Same fencing, very different paddock.

Rectangle Perimeter formula

P = 2(l + w)

Where

$P$ = Perimeter (m)
$l$ = Length (m)
$w$ = Width (m)

Missing one of these? Work it out first, then come back

Perimeter — Square Perimeter, Triangle Perimeter
Length — Rectangle Diagonal, Rectangular Prism Surface Area
Width — Rectangle Diagonal, Rectangular Prism Surface Area