Area & Volume Calculator
Calculate the area or volume of rectangles, circles, triangles, cylinders, spheres and cones with a chosen length unit.
🔒 Runs entirely in your browser — nothing is uploadedFormulas for common shapes
This calculator handles the shapes that come up most often in homework, DIY projects and construction estimates. For two-dimensional shapes it returns area, measured in square units. Rectangle area is length × width. Circle area is π × r², where r is the radius. Triangle area is base × height ÷ 2. Because area multiplies two lengths together, the answer is always expressed in your chosen unit squared, such as cm² or ft².
For three-dimensional shapes it returns volume, measured in cubic units. A cylinder is π × r² × height, a sphere is 4 ÷ 3 × π × r³, and a cone is π × r² × height ÷ 3 — exactly one third of the matching cylinder. Volume multiplies three lengths, so the result is shown in your unit cubed, such as cm³ or in³. The widget only displays the fields a shape needs and relabels them, so you always know whether to enter a radius, a height, a base, a length or a width.
Choosing units and checking results
Keep every measurement in the same unit before you calculate. If a drawing mixes centimetres and metres, convert first, otherwise the squared or cubed result will be far off. The calculator does not convert between units for you; it simply labels the output with the unit you selected raised to the right power. For circular shapes, remember that r is the radius, which is half the full width across the shape — a frequent source of mistakes is entering the diameter instead. Use the formula line under the answer to confirm which equation was applied. All math runs in your browser using standard JavaScript precision, which is accurate for everyday estimating, planning and study.
Worked examples
A cylinder with radius 3 cm and height 10 cm has a volume of π × 3² × 10 = π × 90 ≈ 282.743 cm³. A cone with the same radius and height holds one third of that, about 94.248 cm³. A rectangle 4 m long and 3 m wide covers 12 m², and a circle with a 5 ft radius covers π × 25 ≈ 78.54 ft².
Two quick sanity checks help catch typos. Doubling every length of a shape multiplies its area by 4 and its volume by 8. Because a sphere's volume grows with the cube of the radius, a small error in r is magnified in the result. If you only know the diameter, halve it before entering the value, and round the final answer rather than the intermediate numbers.
How to use
- Choose a shapePick a 2D shape for area or a 3D shape for volume from the list.
- Enter the dimensionsOnly the fields the shape needs are shown. Use the same length unit for every input.
- Read area or volumeThe result updates instantly with the formula and squared or cubed unit.