Cube Surface Area Calculator 2026 | 6a² Formula | OmniCalculator

Free cube surface area calculator. Calculate surface area of cubes using side length, diagonal, or volume. Step-by-step formula 6a² with all 6 faces breakdown.

🎲 Cube Surface Area Calculator

Calculate Surface Area Using 6a² Formula

📐 6 Equal Faces
📏 All Edges Equal
📦 Volume
↗️ Diagonal

Perfect cube calculations made easy

Cube Surface Area Calculator

🎲 Calculate Cube Surface Area
📏From Side Length
↗️From Diagonal
📦From Volume
From Face Area

📏 Enter Side Length

All 12 edges are equal
Quick: 1 2 3 4 5 10 12 15
Total Surface Area
150 cm²
Cube with side = 5 cm
📐
150
Total SA (cm²)
25
Face Area
📏
5
Side Length
📦
125
Volume (cm³)
↗️
8.66
Space Diagonal
7.07
Face Diagonal

🎲 All 6 Faces (Each = a²)

Top
25 cm²
Bottom
25 cm²
Front
25 cm²
Back
25 cm²
Left
25 cm²
Right
25 cm²

📊 Calculation Steps

Side Length (a) 5 cm
Face Area (a²) 25 cm²
Number of Faces 6
Formula 6 × a² = 6a²
Total Surface Area 150 cm²
💡 Quick Formula: For a cube with side a, surface area is simply 6a² — six identical square faces, each with area a².
a a a
Cube (Regular Hexahedron)
6 square faces, 12 equal edges, 8 vertices

Cube Formulas

Surface Area

Surface Area of Cube

Where a = side length (edge length)

Volume

Volume of Cube

Space Diagonal

Space Diagonal (Corner to Opposite Corner)

Face Diagonal

Face Diagonal (Across One Face)

Side from Surface Area

Finding Side Length from Surface Area

Side from Volume

Finding Side Length from Volume

Cube Properties

PropertyValueFormula
Faces6 (all squares)
Edges12 (all equal)
Vertices8
Surface Area6 × face area6a²
VolumeSide cubed
Space DiagonalSide × √3a√3
Face DiagonalSide × √2a√2
Face-to-Volume Ratio6/aSA/V = 6/a

Example Calculations

Side (a)Face Area (a²)Surface Area (6a²)Volume (a³)Diagonal (a√3)
11611.73
242483.46
3954275.20
41696646.93
5251501258.66
10100600100017.32

How to Calculate Cube Surface Area

  1. Measure one edge — All 12 edges of a cube are equal, so measure any one.
  2. Square the side length — Calculate a² to get the area of one face.
  3. Multiply by 6 — A cube has 6 identical faces, so SA = 6 × a².
  4. Include units — Remember to use square units (cm², m², in²).
  5. Verify — Check your answer: Total SA = 6 × (side)².

Educational Resources

Frequently Asked Questions

What is the surface area formula for a cube?+

The surface area of a cube is SA = 6a², where a is the side length (edge). This formula comes from having 6 identical square faces, each with area a².

Why is it 6a² and not just a²?+

Because a cube has 6 faces, not 1. Each face is a square with area a². Total surface area = 6 × a² = 6a². Think of it as wrapping all 6 sides of a box.

What's the difference between a cube and a rectangular prism?+

A cube has all edges equal (l = w = h = a), so all 6 faces are identical squares. A rectangular prism has rectangular faces that may differ. Cube SA = 6a²; Rectangular prism SA = 2(lw + lh + wh).

How do I find the side length from surface area?+

Rearrange the formula: a = √(SA/6). For example, if SA = 150 cm², then a = √(150/6) = √25 = 5 cm.

What is the space diagonal of a cube?+

The space diagonal connects two opposite corners through the interior of the cube. Formula: d = a√3 ≈ 1.732a. For a cube with side 5, diagonal = 5 × 1.732 = 8.66.

What is the face diagonal?+

The face diagonal goes across one square face (corner to corner of a face). Formula: f = a√2 ≈ 1.414a. This is different from the space diagonal which goes through the cube's interior.

How many edges does a cube have?+

A cube has 12 edges, all of equal length. It also has 6 faces (all squares) and 8 vertices (corners).

How do I find surface area from volume?+

First find side length: a = ∛V (cube root of volume). Then calculate SA = 6a². For example, if V = 125 cm³, then a = 5 cm, and SA = 6 × 25 = 150 cm².

Is a cube a Platonic solid?+

Yes! The cube (hexahedron) is one of the five Platonic solids — regular convex polyhedra with identical faces. The others are tetrahedron, octahedron, dodecahedron, and icosahedron.

Is this calculator free?+

100% free! No sign-up required. Calculate cube surface areas unlimited times.

Created by OmniCalculator.space — Your trusted source for free online tools.

Last Updated: January 2026