Area Calculator
Quickly estimate the square footage or square meters of common shapes-rectangles, circles, triangles, trapezoids, and more-or combine sections to get a total footprint. It’s useful for planning flooring or paint coverage, sizing garden beds and patios, estimating roofing or siding, or anytime you need a reliable surface area for budgeting and materials.
The Area Calculator lets you enter known dimensions, switch units, and sum multiple sub-areas to reach a precise total; you can even work backward from a target area to find a matching side length for standard shapes. The goal is to remove guesswork so you order the right amount, control costs, and move from rough sketch to confident plan in seconds.
Choose a shape, enter dimensions, and see the step-by-step area calculation with a clean final result.
Your shape
Preview
Final area
Results interpretation
- Units matter: switching cm → m changes the numeric result by a factor of 10,000 because area is squared.
- Pick the right formula: triangles accept base-height or three sides (Heron). Use the inputs you actually know.
- Check plausibility: zero or negative values aren’t valid dimensions; our tool ignores them.
- Rounding: your decimal places setting only affects display, not the internal math.
How our calculator works
Each shape uses its standard area formula. Inputs are converted to meters internally so we can stay unit-safe; the final answer is converted back to your chosen unit squared.
Show formulas
- Rectangle:
A = w·h - Square:
A = s² - Circle:
A = πr² - Triangle (base/height):
A = ½bh - Triangle (Heron):
A = √[s(s−a)(s−b)(s−c)],s=(a+b+c)/2 - Trapezoid:
A = ½(b₁+b₂)h - Ellipse:
A = πab(semi-axes) - Parallelogram:
A = bh - Sector:
A = (θ/360)πr² - Regular polygon:
A = n s² / (4 tan(π/n))
Area FAQs
What units does the calculator support?
Centimeters, meters, inches, and feet. Results display as squared units (cm², m², in², ft²).
Do I need all triangle sides?
No. Use base + height if that’s easier. Otherwise enter all three sides and we’ll apply Heron’s formula.
Why did my number change so much when I switched units?
Area scales with the square of the conversion factor. For example, 1 m = 100 cm, so 1 m² = 10,000 cm².
Can I calculate irregular shapes?
Approximate by splitting the shape into rectangles/triangles and summing their areas.
What about perimeter?
Our tool focuses on area. Try the Triangle or Circle tools for more geometry features.
Use cases & examples
- Flooring: A 12 ft × 10 ft room → 120 ft² of coverage.
- Round table: Radius 20 in → 1257 in² of surface area.
- Garden bed (trapezoid): Bases 3 m and 4 m, height 2 m → 7 m².
What our Area Calculator does
Our area calculator results help you size materials, compare designs, and check homework quickly. This page supports rectangle, square, circle, triangle (base-height or Heron), trapezoid, ellipse, parallelogram, sector, and regular polygon, with instant feedback as you type.
How to use this tool
Pick your shape, choose units, and enter the dimensions you know. The amber banner shows the steps and the exact formula; the green banner shows the final area in your chosen units. You can change decimal places to control rounding.
Why units matter
Area is two-dimensional. Doubling a length multiplies area by four; converting length units multiplies area by the square of the conversion factor. Keep inputs consistent and use the unit selector for the output.
Common pitfalls
- Using diameter where the formula expects radius (circle).
- Mixing units (inches with centimeters) in one calculation.
- Triangle “height” must be perpendicular to the base.
Limitations
We assume ideal, flat shapes without cutouts. For irregular regions, split into simpler shapes and sum areas.
Explore more calculators related to Geometry
- Square Calculator
Find the area, perimeter, and diagonal of a square quickly and accurately.
- Rectangle Calculator
Calculate the area, perimeter, and diagonal of a rectangle in seconds.
- Triangle Calculator
Solve triangle sides, angles, and area using multiple geometry formulas.