Perimeter Calculator
Calculate the perimeter of a rectangle from length and breadth — pick each measurement's own unit and it converts automatically.
What this calculator does
Calculates the total distance around the outside of a rectangle from its length and breadth, converting between units automatically if the two measurements are given differently (say, one in meters, one in feet).
Who this is for
Anyone fencing or bordering a rectangular space, ordering trim, skirting board, or edging material, working out how much material is needed to go around a room, garden, or plot, or checking a manual perimeter calculation for a homework problem.
How this calculator works
Perimeter = 2 × (Length + Breadth). Since length and breadth are often measured in different units in practice, this calculator converts both measurements to meters internally before adding them, then shows the result in meters, feet, and centimeters.
Worked example
A rectangular garden 5 meters long and 4 meters wide: Perimeter = 2 × (5 + 4) = 2 × 9 = 18 meters. If you needed to fence it and wanted a 10% buffer for gate overlap and cutting waste, you'd budget for roughly 19.8 meters of fencing material.
Common mistakes
- Confusing perimeter with area. Perimeter (linear units, like meters) measures the distance around the edge; area (square units) measures surface covered — use the Area Calculator if you need surface coverage instead.
- Forgetting perimeter only needs two sides for a rectangle. Unlike an irregular polygon where you sum every side individually, a rectangle's perimeter only needs length and breadth since opposite sides are equal.
- Not adding extra for fencing or trim waste. The calculated perimeter is the exact boundary length — real-world materials (fencing, skirting board, trim) usually need 5-10% extra for overlaps, corners, and cutting waste.
- Mixing up which number is length vs breadth. It doesn't actually change the perimeter result (the formula is symmetric), but it matters if you're also calculating area for the same shape, so keep your measurements consistent between the two calculators.
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Frequently Asked Questions
What is the formula for the perimeter of a rectangle?
Perimeter = 2 × (Length + Breadth). For a square, this simplifies to 4 × side length.
What if my length and breadth are in different units?
Pick each measurement's own unit from its dropdown — this calculator converts both to meters automatically before adding them, so mixed units are never a problem.
How much extra material should I buy beyond the calculated perimeter?
A common rule of thumb is 5-10% extra to account for overlaps, corner cuts, and waste, though this varies by material — check supplier guidance for fencing, skirting, or edging specifically.
Calculate the perimeter of your yard's outline, then add roughly 5-10% extra to account for gate posts, corner overlaps, and cutting waste.