Cuboid Calculator

A cuboid, also called a rectangular box or rectangular prism, is the most common solid shape in everyday life, the form of a room, a shipping carton, a brick, a fish tank or a concrete footing, and this calculator works out its key properties from the three measurements that define it: length, width and height. Enter those and it returns the volume, the total surface area, the space diagonal and the combined length of all the edges, updating as you type. The volume is the simplest result of all, just the three dimensions multiplied together, and it tells you the capacity, how much the box holds or how much material fills it. The surface area takes a little more thought, because a cuboid has three pairs of matching rectangular faces, so it is twice the sum of length times width, length times height and width times height; this is exactly what you need when working out paint, wrapping, cladding or sheet material. The space diagonal is the longest straight line that fits inside the box, running corner to opposite corner through the middle, and it comes from a three-dimensional version of Pythagoras, useful for checking whether a long item will fit in a carton or a vehicle. That makes the tool genuinely useful for a huge range of practical jobs: tradespeople estimating concrete or fill, movers and couriers checking capacity and fit, aquarium owners working out water volume, and students learning solid geometry. Because every result updates live, you can adjust any dimension and immediately see the effect on volume, surface and diagonal, which makes it easy to compare options or scale a design. The formulas and a worked example are explained clearly below.

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