---
title: "How to Calculate Area and Perimeter — Formulas for All Common Shapes"
description: "Area and perimeter formulas for squares, rectangles, triangles, and circles — with step-by-step worked examples. Includes metric vs imperial area units and real-world applications."
url: "https://worldcalculators.org/learning/how-to/area-perimeter/"
canonical: "https://worldcalculators.org/learning/how-to/area-perimeter/"
---

# How to Calculate Area & Perimeter

Area and perimeter formulas for squares, rectangles, triangles, and circles — with step-by-step worked examples. Includes metric vs imperial area units and real-world applications.

## Quick answer

Key formulas: Rectangle area = length × width. Circle area = πr². Triangle area = ½ × base × height. Perimeter = sum of all sides (rectangle: 2l + 2w; circle circumference: 2πr). Units: area is always in square units (m², ft², cm²); perimeter is in linear units (m, ft, cm).

## Step-by-Step

Measure the lengths you need for that shape. A rectangle needs length and width (e.g. 8 m × 3 m); a circle needs the radius (e.g. 7 cm); a triangle needs base and perpendicular height.
Use the formula for your shape. Rectangle area = length × width = 8 × 3 = 24 m². Circle area = πr². Triangle area = ½ × base × height.

Source: https://worldcalculators.org/learning/how-to/area-perimeter/
Markdown mirror of the HTML page. Prefer this URL for RAG; the interactive calculator still lives on the HTML page.