Area Calculator

Calculate the area of common geometric shapes and the surface area and volume of 3D solids, right in your browser.

About area calculator

How it works

Pick a shape from the dropdown and the calculator shows only the measurements that shape needs. Enter positive values and it computes the area for flat (2D) shapes, or the surface area and volume for solid (3D) shapes. Everything runs locally in your browser — no data leaves your device.

2D formulas

\begin{aligned} \text{square} &= s^2 & \text{rectangle} &= l \cdot w \\ \text{triangle} &= \tfrac{1}{2} b h & \text{parallelogram} &= b h \\ \text{trapezoid} &= \tfrac{1}{2}(a + b) h & \text{circle} &= \pi r^2 \\ \text{ellipse} &= \pi a b & \text{rhombus/kite} &= \tfrac{1}{2} p q \end{aligned}

Regular polygons (pentagon, hexagon, heptagon, octagon) with $n$ sides of length $s$ :

A = \frac{n\,s^2}{4\,\tan\!\left(\frac{\pi}{n}\right)}

3D formulas

\begin{aligned} \text{sphere} &: SA = 4\pi r^2, & V &= \tfrac{4}{3}\pi r^3 \\ \text{cylinder} &: SA = 2\pi r(r + h), & V &= \pi r^2 h \\ \text{cone} &: SA = \pi r\left(r + \sqrt{r^2 + h^2}\right), & V &= \tfrac{1}{3}\pi r^2 h \\ \text{cube} &: SA = 6 s^2, & V &= s^3 \\ \text{cuboid} &: SA = 2(lw + lh + wh), & V &= l w h \end{aligned}

For the cone and square pyramid the slant height is derived from the perpendicular height using the Pythagorean theorem, so you only enter the height you can measure.

When to use it

Homework and geometry practice
Estimating materials for flooring, painting, or fabric
Quick sanity checks on engineering or construction measurements
Comparing the capacity (volume) of containers and tanks