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Cube and Box Calculator: Volume and Surface Area

This free calculator finds the volume, surface area and diagonals of a cube or a rectangular box. For a cube, enter the same number three times. It also converts the volume to litres.

By Debmedia Technologies LLP · Kolkata, India · Updated

What Is It and When Do You Need It?

Boxes, rooms, tanks and cartons are all cuboids. Their volume tells you how much they hold and their surface area how much material covers them.

Enter the three sizes.

How to Use This Tool

  1. Enter the value or values asked for in the boxes.
  2. Choose the unit label if there is a choice.
  3. Press Calculate.
  4. Read every result in the table and copy what you need.

How the Calculation Works

Volume = lwh. Surface area = 2(lw + lh + wh). The face diagonals are √(l² + w²), √(l² + h²) and √(w² + h²), and the space diagonal is √(l² + w² + h²). A cube is the case l = w = h.

Worked Example

A box 2 by 3 by 6 has a volume of 36, a surface area of 72 and a space diagonal of 7.

Common Uses

  • Packaging and shipping.
  • Tanks and aquariums.
  • Room volume.
  • Homework.

Tips and Common Mistakes

  • Use one unit for all three sizes.
  • Check the longest item fits the space diagonal.
  • Volume is in cubic units.
  • Measure carefully: a small error in a length is squared in an area and cubed in a volume, so a 5 percent error in a side can become a 10 percent error in the area or a 15 percent error in the volume.
  • Round only at the end. If you copy a result into another calculation, copy the full number from the tool rather than a rounded one, so small errors do not build up.

Next, you may need the rectangle calculator, pyramid calculator, cylinder calculator, sphere calculator.

Everything runs in your browser. Nothing you type is uploaded, stored or sent to any outside service.

Frequently Asked Questions

Volume = l × w × h, surface area = 2(lw + lh + wh) and space diagonal = √(l² + w² + h²).
Enter the side length in all three boxes.
The longest straight line inside the box, from one corner to the opposite corner.
If the sizes are in centimetres, divide the volume by 1,000. If they are in decimetres, the volume is already in litres.

Disclaimer: results are calculated in your browser from the numbers you enter. Check important results before you rely on them for money, health, safety or legal decisions.