Area Calculator

Expert Reviewed — Verified by Dr. Priya Nair, PhD, Applied Mathematics · Published Author on Geometric Analysis
NIST-Standard Formulas Updated August 2026
▭ Rectangle Area Calculator
Formula Area = Length × Width  |  Perimeter = 2 × (Length + Width)
l w
Rectangle
△ Triangle Area Calculator (Heron's Formula)
Heron's Formula s = (a+b+c)/2  |  Area = √[s(s-a)(s-b)(s-c)]
a,b,c
Triangle
⬡ Trapezoid Area Calculator
Formula Area = ½ × (Base₁ + Base₂) × Height
b₁ b₂ h
Trapezoid
○ Circle Area Calculator
Formula Area = π × r²  |  Circumference = 2π × r
r
Circle
◔ Sector Area Calculator
Formula Area = (θ/360) × π × r²  (degrees)  |  Arc Length = r × θ (radians)
r θ
Sector
⬭ Ellipse Area Calculator
Formula Area = π × a × b  |  Perimeter ≈ π × [3(a+b) − √((3a+b)(a+3b))] (Ramanujan)
a b
Ellipse
◧ Parallelogram Area Calculator
Formula Area = Base × Height (perpendicular height)
b h
Parallelogram
🔬 Expert Review — Area Formulas & Geometric Accuracy
PN

Dr. Priya Nair, PhD

Applied Mathematics · Geometric Analysis · 16 Years · University of Cambridge

"The area formulas implemented in this calculator follow the standard definitions from Euclidean geometry. Rectangle area is simply length × width. Triangle area uses Heron's formula — a proven method requiring only three side lengths, computing semi-perimeter s=(a+b+c)/2, then Area=√[s(s-a)(s-b)(s-c)]. Circle area (πr²) and sector area ((θ/360)×πr²) use the NIST-standard value of π=3.14159265358979. Ellipse area (π×a×b) and the Ramanujan approximation for ellipse perimeter are the industry-standard methods. Unit conversions use exact SI multipliers — no approximation. Note: for triangles, all three sides must satisfy the triangle inequality (sum of any two sides must exceed the third)."

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Verified August 2026: All 7 shape formulas verified against NIST Handbook of Mathematical Functions (DLMF) and ISO 80000-2 standard for mathematical notation. Unit conversions use exact SI factors per NIST Guide SP 811.
AS

Ananya Singh

Mathematics Content Writer · StudyHub · BSc Statistics & Mathematics, Delhi University

Ananya specializes in geometry, mensuration, and applied mathematics content for students and professionals. She has developed comprehensive guides on area calculation methods for architecture, engineering, agriculture, and everyday land measurement applications, with a focus on real-world US use cases including square footage for home renovation, plot area for real estate, and land area in acres and hectares.

Comprehensive Area Calculator & Geometric Formulas

Whether you are trying to calculate the square footage of an acre for a real estate purchase, figure out the formula for finding the area of a triangle for a geometry test, or determine how much paint you need for a wall, you are working with Area.

Area is the measure of 2-dimensional space contained within a closed boundary. Our area calculator acts as a unified geometric engine, allowing you to instantly compute the area of seven different geometric shapes: rectangles, triangles, trapezoids, circles, sectors, ellipses, and parallelograms. It also serves as a robust square footage calculator and unit converter.


Part 1: How to Use the Area Calculator

Our tool goes beyond simple math by offering a dynamic, multi-unit calculation matrix.

Step-by-Step Instructions
  1. Select Your Shape: Use the navigation tabs to choose the geometric shape you are working with (e.g., Circle, Trapezoid).
  2. Input Your Dimensions: Enter your measurements.
  3. Mix and Match Units: This is the most powerful feature of the calculator. You can enter one dimension in feet and another in meters! The calculator will mathematically normalize the units before processing the formula.
  4. View the Results: The calculator outputs a massive conversion matrix. If you calculate an area in square meters, the tool instantly shows you that exact same area in square feet, square yards, acres, and hectares simultaneously.
The Square Footage Calculator

A massive percentage of users search for a calc sq ft or square footage calculator for home renovation projects (flooring, roofing, painting). * How to do it: Select the "Rectangle" tab. Enter your room's Length in feet and Width in feet. * Example: A room that is 15 feet long and 12 feet wide has an area of 180 square feet (15 × 12). * Convert acre to sq ft: If you are buying land, you often need to know how big an acre is. Our calculator natively handles this conversion. (For reference, the square footage of an acre is exactly 43,560 sq ft).


Part 2: 2-Dimensional Area Formulas

If you are a student looking for the formula of maths for your homework, here is the complete breakdown of the mathematical formulas powering our calculator.

1. Formula to Calculate Area of Rectangle

The most basic of all geometric formulas. A rectangle is a quadrilateral with four right angles. * Formula: Area = Length × Width * Perimeter Formula: Perimeter = 2 × (Length + Width)

2. Triangle Area Formula

Our calculator uses Heron's Formula, which is incredibly powerful because it allows you to calculate the area of any triangle simply by knowing the lengths of its three sides, without needing to know the height! * Heron's Formula: Area = √[s(s - a)(s - b)(s - c)] * (Where 's' is the semi-perimeter: s = (a + b + c) / 2)

3. Area of a Circle Formula

A circle is a shape consisting of all points in a plane that are at a given distance (the radius) from a given center point. * Area Circle Formula: Area = π × r² (where r is the radius) * Calculating Circumference (Perimeter): Circumference = 2 × π × r

4. Trapezoid Formula

A trapezoid is a quadrilateral with at least one pair of parallel sides (the bases). * Area Formula: Area = [(a + b) / 2] × h * (Where 'a' and 'b' are the parallel bases, and 'h' is the height)

5. Sector Area Formula

A sector is a portion of a circle enclosed by two radii and an arc (like a slice of pizza). * Area Formula (Degrees): Area = (θ / 360) × π × r²

6. Ellipse Area Formula

An ellipse is essentially a stretched circle, defined by a major axis and a minor axis. * Area Formula: Area = π × a × b * (Where 'a' is the semi-major axis and 'b' is the semi-minor axis)

7. Parallelogram Area Formula

A parallelogram is a quadrilateral with two pairs of parallel sides. * Area Formula: Area = Base × Height


Part 3: From Area to Volume (3-Dimensional Space)

Many users looking for an area calculator actually need to calculate Volume. While Area measures 2-dimensional space (Length × Width), Volume measures 3-dimensional space (Length × Width × Height) to determine capacity.

While we offer a dedicated Volume Calculator, here are the formulas for the most highly searched 3D objects, so you can manually calculate them using your 2D area results:

Formula for Volume of a Cylinder

A cylinder is essentially a circle stretched upward. To find its volume, you simply find the area of the circular base and multiply it by the height. * Volume of a Cylinder: V = π × r² × h * Application: Use our Circle calculator to find the area of the base, then multiply that result by your tank's height.

Cone Volume Formula

A cone is structurally related to a cylinder, but it narrows to a point. Its volume is exactly one-third the volume of a cylinder with the same base and height. * Formula: V = (1/3) × π × r² × h

Formula for the Volume of a Sphere

A sphere is a perfectly round 3D object (like a basketball). * Formula: V = (4/3) × π × r³

Triangular Prism Volume Formula

A triangular prism is a 3D shape with two triangular bases. * Formula: V = Area of Triangular Base × Length * Application: Use our Triangle calculator (Heron's formula) to find the area of the base, then multiply by the length of the prism.


Part 4: Frequently Asked Questions (FAQs)

How do you convert feet into meters?

To convert feet to meters, multiply the length in feet by 0.3048. To convert meter into foot, multiply the length in meters by 3.28084. Our calculator handles this conversion natively in the dropdown menus.

How do I calculate the area of an irregular shape?

There is no single formula for an irregular polygon. You must split the irregular shape into smaller, regular shapes (like a rectangle and a triangle), calculate the area of each shape individually using our calculator, and then add those areas together.

What is the formula for perimeter?

Perimeter is the total length of the outside boundary of a shape. It is a 1-dimensional measurement (unlike area, which is 2D). For polygons (rectangles, triangles), the formula for perimeter is simply adding the lengths of all the outside sides together. For a circle, the perimeter is called the circumference.

Why is area squared?

Area is always expressed in "square" units (e.g., square feet, square meters) because you are multiplying two 1-dimensional measurements together. Multiplying feet by feet mathematically results in feet squared (ft²).


Start Calculating Now

Whether you need to measure a distance on Google Maps and calculate the acreage of a land parcel, or you just need a reliable calculator feet and inches tool for your weekend woodworking project, select your shape above and get instant, perfectly accurate geometric results.

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