GeomBench

Perimeter Calculator

The distance around a rectangle from width and height.

Width

Height

Perimeter

P = 2(w + h)

Area: 40

What you entered

Width: 8Height: 5

1
Area
8 × 5= 40
2
Perimeter
2 × (8 + 5)= 26
3
Diagonal
√(8² + 5²)= 9.434

Result

Perimeter: 26

A 8 × 5 rectangle has a perimeter of 26.

Perimeter and area for common room and yard sizes

Perimeter is the distance once around the edge, calculated as P = 2 x (width + height). Area is shown alongside because the calculator returns both, and the two are easy to mix up when ordering materials.

Rectangle	Width (ft)	Height (ft)	Perimeter (ft)	Area (sq ft)
Calculator default	8	5	26	40
Small bedroom	10	10	40	100
Standard bedroom	12	10	44	120
Square room	12	12	48	144
Living room	15	12	54	180
Single garage	20	15	70	300
Small back yard	30	20	100	600
Mid-size yard	40	30	140	1,200
Large yard	50	30	160	1,500
Half-acre plot side	100	50	300	5,000

The calculator has no unit attached, so the same numbers hold for metres: 8 by 5 metres is a 26 metre perimeter. Buy fencing, trim or edging by the perimeter figure and paint, sod or flooring by the area figure. Subtract gate or doorway widths from the perimeter before ordering, and add a waste allowance for anything cut to fit.

Perimeter is about the boundary, not the inside

Where area tells you how much surface something covers, perimeter tells you how much material traces its edge — fencing, trim, or the wire around a garden bed.

A common mix-up

It's easy to accidentally compute area when you need perimeter (or vice versa) — always double-check which one your project actually calls for before ordering materials.

Frequently asked questions

How do I calculate the perimeter of a rectangle?

Perimeter = 2 × (length + width). A yard 30 feet by 20 feet needs P = 2 × (30 + 20) = 100 feet of fencing. Perimeter measures the total boundary — the distance you'd walk going around the edge once.

How much fencing do I need for my yard?

Measure each side of the yard in feet and add them up. For a rectangular yard: P = 2(length + width). Subtract any gates or openings. A 50×30 yard = 160 linear feet of fencing minus any gap for a gate.

What is the difference between perimeter and area?

Perimeter is the distance around the edge (measured in feet, meters — linear units). Area is the space inside (measured in square feet, square meters). Perimeter is for buying fencing, trim, or border. Area is for buying paint, carpet, or sod.