Cube Calculator
From a single side length, get the volume, the surface area, and both diagonals — every number that describes a cube.
One side, four answers
Enter the side length and the calculator returns the volume (s³), the surface area (6s²), the face diagonal (s√2), and the space diagonal (s√3) at once.
Keep units consistent
The side is unit-agnostic — your answers come back in the same unit (squared for the surface, cubed for the volume), so don't mix centimetres with inches.
What is a cube calculator?
Side in, full cube out
A cube calculator turns one measurement — the side length, the length of any edge — into the numbers that describe the whole solid: its volume, its surface area, and its two diagonals. A cube is the special box where length, width, and height are all equal, so a single value fixes everything. That makes the side the only input you need for dice and storage boxes, packaging and shipping cartons, sugar cubes and building blocks, or any geometry homework where a cube shows up.
Enter the side length in any length unit to get the volume, surface area, and diagonals instantly.
Four short formulas, all built from the side length s.
volume = s³The volume is the side cubed (s × s × s). The surface area covers all six identical faces, so it is 6 × s². The face diagonal runs across one square face and equals s × √2, while the space diagonal cuts straight through the middle of the cube from corner to corner and equals s × √3. Because the volume uses the third power of the side, it grows far faster than the surface area or the diagonals as the cube gets bigger.
Suppose you have a cube with a side of 3.
Volume
3³ = 3 × 3 × 3 = 27 cubic units — the space inside.
Surface area
6 × 3² = 6 × 9 = 54 square units — all six faces together.
Face diagonal
3 × √2 = 4.242641 — across one square face.
Space diagonal
3 × √3 = 5.196152 — corner to corner through the inside.
The four outputs answer four different everyday questions. The volume (27 for a side of 3) is how much the cube holds — the sugar, sand, or water that fits inside, or the space a shipping carton occupies. The surface area (54) is the material you would need to paint, wrap, or cover all six faces. The face diagonal (about 4.242641) is the longest straight line across one side, and the space diagonal (about 5.196152) is the longest line that fits anywhere inside the cube — the measurement that tells you whether a thin rod will fit corner to corner. The key insight is that a cube is simply the box with all sides equal, and its volume grows with the cube of the side: double the side from 3 to 6 and the volume jumps eightfold, from 27 to 216, while the surface area only quadruples. That is why a slightly bigger storage box holds far more than it looks, and why doubling a die makes it feel surprisingly heavy.
The formulas are exact, but a couple of practical points are worth keeping in mind.
Perfect cubes and consistent units
These formulas describe a perfect cube with all edges equal and all angles square. Real objects — a box that is slightly taller than it is wide, a carton with rounded corners, a block with wall thickness — will differ from the computed value; for those, use a rectangular-prism calculator instead. The side is also unit-agnostic, so the answers are only meaningful if you keep one unit throughout: a side in centimetres gives a surface in square centimetres and a volume in cubic centimetres, never a mix.