Cube Volume and Surface Area Calculator
The volume of a cube is V = s³ and its surface area is 6s², and this cube calculator works out both the moment you type one side length. Since every edge of a cube is equal, a single number gives you the volume, the surface area, the face and space diagonals, and the answer in liters, gallons, and cubic units. It's a special rectangular prism with all sides the same, and the calculator shows the formulas and steps with every result.
- Volume V = s³
- Surface area 6s²
- Face & space diagonal
- One side input
- 14 output units
Last updated June 15, 2026 Method: V = s³, SA = 6s² Reviewed by the Calcowa math team
Enter a positive side length to see the results.
Show all volume units
V = 4³ = 64 in³ · SA = 6 × 4² = 96 in²
What is a cube?
A cube is a box with six identical square faces, twelve equal edges, and eight corners, where every angle is a right angle. A dice, a sugar cube, and a Rubik's cube are everyday examples. Because all the edges share one length, you only need a single measurement to size it.
A cube is a special rectangular prism, or cuboid, with the length, width, and height all equal. That's why the box volume rule l × w × h becomes s × s × s = s³, and the surface area becomes 6 square faces.
Volume of a cube
The volume of a cube is V = s³, the side length cubed. You multiply the edge by itself twice, which counts how many unit cubes fit inside. For a cube with 5 cm sides, the volume is 5 × 5 × 5 = 125 cubic centimeters. Since the cube is the most regular box there is, this single step is all the volume formula for a cube ever needs.
Surface area of a cube
The surface area of a cube is SA = 6s², because a cube has six identical square faces and each face has area s². Work out one face, then multiply by six. For a 5 cm cube, that's 6 × 25 = 150 square centimeters. The calculator shows the surface area beside the volume, so you'll have both the inside and the outside of the cube from one number.
How do you calculate the volume of a cube?
To find the volume of a cube, measure one edge and cube it. Here's the full sequence:
- 1
Measure one sideMeasure the length of a single edge, since they are all equal.
- 2
Cube the sideMultiply the side by itself twice: s × s × s.
- 3
Read the volumeThat's the volume of the cube in cubic units.
- 4
Find the surface areaFor the outside, multiply one face by six: 6 × s².
- 5
Convert the unitsConvert to liters, gallons, or cubic feet if that's what you need.
Diagonal of a cube
A cube has two kinds of diagonal. The face diagonal runs across one square face and measures s√2. The space diagonal runs from one corner straight through the middle to the opposite corner, and it measures s√3. For a 4-inch cube, that's a face diagonal of about 5.66 inches and a space diagonal of about 6.93 inches. The calculator shows the space diagonal beside the volume.
Find the side from the volume or surface area
Sometimes you know the volume or the surface area and need the edge. Just rearrange the formulas. From the volume, the side is the cube root: s = ∛V. From the surface area, the side is s = √(SA ÷ 6). And from the space diagonal, s = d ÷ √3. Once you've got the side, type it into the calculator above and every other measure of the cube follows.
A cube example, step by step
Say you've got a storage cube with 30 cm sides. Cube the side for the volume, then take one face times six for the surface area.
V = 30³ = 27,000 cm³ · SA = 6 × 30² = 5,400 cm²
that's 27 liters, or about 7.13 US gallons
Type a side of 30 in centimeters above, and you'll get the matching liters, gallons, and diagonals at once.
Units and accuracy
Calcowa shows the cube volume in liters, US and UK gallons, milliliters, fluid ounces, and cubic mm, cm, m, inches, feet, and yards all at once, with the surface area in matching square units. Enter the side in any supported unit, and you'll get exact conversions, so the result fits packing, storage, and school work alike.
| Unit | Best for | Good to know |
|---|---|---|
| Cubic inches (in³) | Dice, boxes, small blocks | Default when you enter inches |
| Cubic feet (ft³) | Storage cubes, crates | 1 ft³ = 1,728 in³ |
| Liters (L) | Containers and capacity | 1 L = 1,000 mL |
| US gallons (gal) | Tanks and bins | 1 US gallon = 3.785 L |
| Cubic yards (yd³) | Concrete, soil, large fills | 1 yd³ = 27 ft³ |
Frequently asked questions
Is a cube a rectangular prism?
Yes. A cube is a special rectangular prism, or cuboid, with all three sides equal. That's why its volume rule l × w × h simplifies to s × s × s = s³, and all six faces come out the same size.
The volume of a cube is V = s³, the side length multiplied by itself three times. For a cube with 4-inch sides, that's 4 × 4 × 4 = 64 cubic inches. Because all edges are equal, you only need one measurement.
The surface area of a cube is SA = 6s², since a cube has six identical square faces and each one has area s². For a 4-inch cube, that's 6 × 16 = 96 square inches.
Measure one edge, then cube it: multiply the side by itself twice. A cube is the simplest solid for this because every side is the same, so V = s × s × s with a single number.
A cube has two diagonals. The face diagonal across one square is s√2, and the space diagonal from corner to opposite corner through the middle is s√3. For a 4-inch cube, the space diagonal is about 6.93 inches.
Rearrange the formulas. From the volume, the side is the cube root: s = ∛V. From the surface area, s = √(SA ÷ 6). Either one gives you the edge length, and then every other measure follows.
Yes. A cube is a special rectangular prism, or cuboid, where all three sides are equal. That's why the box rule l × w × h becomes s × s × s = s³ for a cube.
Cube the side for the volume in cubic units, then read the litres or gallons line. The calculator shows litres, US and UK gallons, and millilitres beside the cubic result, so there's no manual conversion.
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