2D Shape Calculators
Free area and perimeter calculators for circles, rectangles, squares, and triangles. Multiple input methods, all formulas shown.
2D Shape Calculators - Area, Perimeter, and Dimensions for Every Flat Shape
Two-dimensional shape calculations appear in construction (floor area, tile count), landscaping, design, education, and everyday problem-solving. These calculators support multiple input combinations so you can work with whatever measurements you have available.
Four 2D Shape Calculators
Circle Calculator - Enter any one known value (radius, diameter, circumference, or area) and get all others instantly. Area = πr², Circumference = 2πr. Also shows sector area and arc length for a given central angle. Used for circular garden beds, cylindrical cross-sections (pair with the Cylinder Calculator), wheels, and pipes.
Rectangle Calculator - Enter length and width to get area, perimeter, and diagonal (using the Pythagorean theorem: d = √(l² + w²)). Or enter area and one side to find the other. Used for room area, plot sizes, screen dimensions, and material cutting plans.
Square Calculator - Enter side length to get area (s²), perimeter (4s), and diagonal (s√2). Works in reverse: enter area to find side length. Used for square tiles, floor sections, and square land parcels.
Triangle Calculator - Three input methods: (1) base and height → Area = ½ × base × height, (2) all three sides → Heron’s formula, (3) two sides and included angle → Area = ½ab·sin(C). Also computes perimeter and identifies triangle type. For angle-based work, combine with the Sin Cos Tan Calculator.
Real-World Applications
Flooring - Use the Rectangle Calculator for room area, divide by tile size, add 10% for cuts and wastage. Circular structures - The Circle Calculator handles round garden beds, pools, and cross-sections. Land measurement - Area outputs are available in square metres, square feet, and square yards for Indian plot conventions.
Frequently Asked Questions
How do I calculate the area of an irregular shape?
Decompose the shape into basic components. Calculate each area separately with the appropriate calculator - Rectangle, Triangle, Circle - and sum the results.
What is Heron's formula and when should I use it?
Heron's formula calculates triangle area when all three side lengths are known: semi-perimeter s = (a+b+c)÷2, then Area = √(s(s−a)(s−b)(s−c)). Use it when you can measure the three sides directly but not the height. Available in the Triangle Calculator.
How many tiles do I need for a given area?
Find floor area with the Rectangle Calculator. Divide by tile area. For a 15 m² room with 30×30 cm tiles (0.09 m²): 15 ÷ 0.09 = 167 tiles. Add 10–15% extra for cuts and breakage.
What is the diagonal of a rectangle?
Diagonal = √(length² + width²) by the Pythagorean theorem - computed automatically by the Rectangle Calculator. For right-angle verification on a building site, use the Pythagorean Theorem Calculator.