What is an area calculator?
An area calculator computes the area—the amount of space inside a two-dimensional shape—for various geometric figures. Area is always measured in square units: square meters, square feet, square inches, and so on. This calculator supports six common shapes: rectangle, square, circle, triangle, parallelogram, and trapezoid. You select a shape, enter the required dimensions (such as length and width, radius, or base and height), and the tool gives you the area and the formula used. No sign-up or download is required; it runs in your browser and is useful for homework, construction, landscaping, and any task where you need to find area quickly.
Understanding area is fundamental in geometry and in many real-world applications. Whether you are measuring a room for flooring, a circular garden for turf, or a triangular plot for planting, an area calculator saves time and reduces errors. This free area calculator works with the same units you enter: if your dimensions are in feet, the result is in square feet; if in meters, the result is in square meters. Just keep all measurements in one unit for consistent results.
How to use this area calculator
First, choose the shape from the dropdown: Rectangle, Square, Circle, Triangle, Parallelogram, or Trapezoid. The input fields update to match the shape. For a rectangle, enter length and width. For a square, enter the side length (one value). For a circle, enter the radius. For a triangle or parallelogram, enter base and height. For a trapezoid, enter base 1, base 2, and height. All values must be positive numbers. When the inputs are valid, click Get result to see the area in square units and the formula used. The calculator displays the result and the formula so you can verify or learn the relationship. Change the shape or dimensions anytime and click Get result again for a new calculation.
Area formulas by shape
Rectangle: Area = length × width. Multiply the two perpendicular sides. Square: Area = side² (or side × side). A square is a rectangle with equal length and width. Circle: Area = π × radius², where π (pi) is approximately 3.14159. The radius is the distance from the center to the edge. Triangle: Area = ½ × base × height. The height is the perpendicular distance from the base to the opposite vertex. Parallelogram: Area = base × height. Again, height is perpendicular to the base, not the slanted side. Trapezoid: Area = ½ × (base₁ + base₂) × height. The two bases are the parallel sides; height is the perpendicular distance between them. This area calculator applies the correct formula for the shape you select.
Understanding area vs perimeter and volume
Area measures the amount of 2D space inside a shape’s boundary. It is different from perimeter (the distance around the shape) and from volume (the amount of 3D space inside a solid). For example, a rectangle 5 units by 3 units has area 15 square units and perimeter 16 units. A circle with radius 5 has area π × 25 ≈ 78.54 square units and circumference 2π × 5 ≈ 31.42 units. When you need to cover a surface—paint, flooring, grass—you use area. When you need to fence or border something, you use perimeter. This calculator focuses on area; for perimeter or volume, use dedicated tools.
Common area calculations and examples
Rectangle: A room 10 feet by 12 feet has area 10 × 12 = 120 square feet. Square: A square with side 5 meters has area 25 square meters. Circle: A circle with radius 5 meters has area π × 25 ≈ 78.54 square meters. Triangle: A triangle with base 8 cm and height 6 cm has area ½ × 8 × 6 = 24 square cm. Parallelogram: Base 10 units and height 7 units give area 70 square units. Trapezoid: Bases 6 and 10 units with height 4 units give area ½ × (6 + 10) × 4 = 32 square units. You can enter these values in the calculator to verify and see the formulas in action.
Units and consistency
Area is always in square units of whatever linear unit you use. If you enter length and width in meters, the area is in square meters (m²). If you enter in feet, the area is in square feet (ft²). If you enter in inches, the area is in square inches (in²). Never mix units in one calculation—for example, do not use length in feet and width in meters. Convert one to match the other first. For large areas, square kilometers (km²), acres, and hectares are common; convert your dimensions to the desired unit before entering, or convert the result afterward using an area converter.
Applications of area calculations
Area calculations are used in construction (flooring, paint, roofing), landscaping (lawn, garden beds, mulch), real estate (property size, lot area), manufacturing (material cutting, coverage), agriculture (field size, crop planning), and design (room layout, furniture placement). Knowing the area helps you order the right amount of material, estimate cost, and plan projects. This area calculator gives you instant results for six common shapes so you can focus on measuring accurately and applying the numbers to your project.
Tips for accurate area results
Measure dimensions with a tape measure, ruler, or other appropriate tool. For rectangles and squares, measure length and width at right angles. For circles, measure the radius (from center to edge) or measure the diameter and divide by 2. For triangles and parallelograms, the height must be perpendicular to the base—do not use the length of a slanted side. For trapezoids, measure both parallel bases and the perpendicular height between them. Double-check that all values are in the same unit before clicking Get result. The calculator does the math; accurate inputs give accurate areas.
Summary
This area calculator finds the area of rectangles, squares, circles, triangles, parallelograms, and trapezoids. Select a shape, enter the required dimensions in the same units, and click Get result to see the area in square units and the formula used. The tool is free, runs in your browser, and requires no account. Use it for homework, construction, landscaping, or any area calculation. Keep units consistent and measure carefully for best results.