A focused calculator for the surface area of a rectangular prism (a box shape) — length, width, and height in, total surface area out.
How it works
The areas of all three pairs of opposite faces are summed: length×width, length×height, and width×height, each counted twice.
What this does not include
This does not include other 3D shapes — for cubes, spheres, cylinders, and cones, use this site’s general surface area calculator instead.
How to use this calculator
- Enter the length, width, and height of the box.
A worked example
A box 3 × 4 × 5: surface area = 2(lw + lh + wh) = 2(12+15+20) = 94.
A cube 2 × 2 × 2: surface area = 24 — six equal square faces of area 4 each.
What the variables mean
| Variable | Meaning |
|---|---|
| Length, width, height | The box’s three dimensions |
Edge cases worth knowing
A cube is just a special case where all three dimensions match — the formula still applies unchanged, simplifying naturally to 6 × side².
A dimension of zero flattens the box into a flat rectangle with a different, simpler area formula, so the calculator declines to show a result rather than a misleading one.
Frequently asked questions
What’s a real-world use for this calculation?
Estimating how much material (wrapping paper, cardboard, paint) is needed to cover a box-shaped object entirely.
Does a cube use the same formula?
Yes — a cube is just a rectangular prism where length, width, and height are all equal, and the formula reduces to 6 × side² in that case.
What’s the difference between this and volume?
Surface area measures the total area of the outer faces; volume measures the space enclosed inside — two different (though related) measurements.
