MATH · AREA
Area Calculator
Calculate the area of a circle, rectangle, triangle, trapezoid, ellipse, or parallelogram. Shows the formula used for each shape.
About This Calculator
Find the area of six common geometric shapes with one calculator. Choose your shape, enter its dimensions, and get the exact area along with the formula — useful for math homework, construction planning, or general geometry work.
How It Works
Select the shape from the dropdown, then enter the required dimensions. Each shape uses a different formula: circles use π·r², rectangles use l·w, triangles use ½·b·h, trapezoids use ½·(a+b)·h, ellipses use π·a·b, and parallelograms use b·h. Results are rounded to 4 decimal places.
The Formula
Circle: A = π × r² Rectangle: A = l × w Triangle: A = ½ × b × h Trapezoid: A = ½ × (a + b) × h Ellipse: A = π × a × b Parallelogram: A = b × h
- r
- radius (circle)
- l, w
- length and width (rectangle)
- b, h
- base and height (triangle, parallelogram)
- a, b
- parallel sides (trapezoid) or semi-axes (ellipse)
Frequently Asked Questions
- What is the area of a circle with radius 7?
- A = π × 7² = π × 49 ≈ 153.9380 square units. Use the circle calculator option and enter 7 as the radius.
- How do I find the area of a triangle without the height?
- If you know all three sides, use Heron's formula — the triangle calculator handles SSS mode. The area-calculator's triangle mode requires base and perpendicular height.
- What is the difference between a parallelogram and a rectangle?
- Both use the formula A = b × h (base × height). For a rectangle, the height equals the side length because all angles are 90°. For a parallelogram with non-right angles, the height is the perpendicular distance between the parallel bases, not the slant side length.
- What are the semi-axes of an ellipse?
- An ellipse has two axes — the major (longer) and minor (shorter). Semi-axis a is half the major axis length, and semi-axis b is half the minor axis length. For a circle, a = b = r.