Area Calculator
Find the area of a rectangle, triangle, circle, trapezoid, ellipse, sector, polygon and more, with the formula shown and results in every unit.
Formula: A = length × width
| Unit | Area |
|---|---|
| square inches | 17,280 |
| square feet | 120 |
| square yards | 13.33333 |
| acres | 0.002754821 |
| square miles | 4.3044e-6 |
| square centimeters | 111,483.6 |
| square meters | 11.14836 |
| hectares | 0.001114836 |
| square kilometers | 1.1148e-5 |
What Area Calculator Does
This area calculator covers twelve shapes in one place (rectangle, square, triangle by base and height or by three sides, circle, ellipse, trapezoid, parallelogram, rhombus, circle sector, regular polygon and ring) and shows the formula with your numbers substituted so you can check the working.
Enter measurements in any length unit, from millimeters to miles. The area is given in that unit squared and converted into square inches, feet and yards, acres, square miles, square centimeters and meters, hectares and square kilometers, so you do not need a separate converter.
How to Use Area Calculator
- Choose a shape from the list
- Pick the unit your measurements are in
- Enter each measurement
- Read the area with the formula and your numbers substituted
- Use the table for the same area in other units
Formula Used by Area Calculator
Core formulas
Rectangle: l × w · Triangle: ½ × b × h · Circle: π × r² · Trapezoid: ½ × (a + b) × h
Worked example
A trapezoid with parallel sides 6 m and 10 m, 4 m apart.
- ½ × (6 + 10) × 4
- = 8 × 4
Result: 32 m² (344.4 ft²).
Regular polygon
A = n × s² ÷ (4 × tan(π ÷ n))
- n
- Number of equal sides
- s
- Length of one side
Worked example
A regular hexagon with 4 ft sides.
- 6 × 16 ÷ (4 × tan(30°))
- 96 ÷ (4 × 0.5774)
Result: 41.57 ft².
Area Unit Conversions
| Unit | Equals |
|---|---|
| 1 square foot | 144 square inches = 0.0929 m² |
| 1 square yard | 9 square feet = 0.8361 m² |
| 1 acre | 43,560 square feet = 4,046.86 m² |
| 1 square mile | 640 acres = 2.59 km² |
| 1 square meter | 10.764 square feet |
| 1 hectare | 10,000 m² = 2.471 acres |
How to Read Your Result
Height means perpendicular height
For triangles, parallelograms and trapezoids, the height is measured at a right angle to the base, not along a slanted side. If you only know the side lengths of a triangle, use the three-sides option, which applies Heron’s formula.
Squared units grow fast
Converting area is not the same as converting length. There are 3 feet in a yard but 9 square feet in a square yard, and 10,000 square centimeters in one square meter. Mixing these up is a common source of large errors in material orders.
Limitations & Accuracy Notes
- Irregular shapes need to be split into standard shapes and added; there is no free-form drawing.
- Results use double-precision arithmetic and are shown to about seven significant figures.
Frequently Asked Questions
How do you calculate area?
Area measures the flat space inside a shape, in square units. For a rectangle multiply length by width; for a triangle take half the base times the height; for a circle multiply π by the radius squared. Pick the shape and the calculator applies the right formula.
How do I find the area of a triangle with three sides?
Use Heron’s formula. Find s, half the perimeter, then area = √(s(s − a)(s − b)(s − c)). For sides 5, 6 and 7: s = 9 and area = √(9 × 4 × 3 × 2) = √216 ≈ 14.70.
What is the area of a circle?
A = πr². A circle with a 4 ft radius (8 ft across) has an area of π × 16 ≈ 50.27 square feet. If you know the diameter, halve it first.
How do I convert square feet to square meters or acres?
One square foot is 0.092903 square meters, and one acre is 43,560 square feet. The calculator converts the result into square inches, feet, yards, acres, square miles, square meters, hectares and square kilometers at once.
How do I find the area of an irregular shape?
Split it into rectangles, triangles and circle pieces, find each area, and add them up (or subtract cut-outs). For rooms, the square footage calculator lets you add several sections.
Why are area units squared?
Because area is two lengths multiplied together. A 3 ft × 3 ft square is 9 square feet, and since 1 yard = 3 feet, 1 square yard = 9 square feet rather than 3.