Thermal Expansion Calculator

How to use the Thermal Expansion Calculator

1. 1Enter the length, the material and the start and end temperatures.
2. 2Pick the units or options from the menus if the thermal expansion tool offers them.
3. 3Read the thermal expansion in the large result box.
4. 4Look at the extra rows for related figures.
5. 5Press Copy result to keep the answer.

When you need the thermal expansion

Builders and engineers use it to place expansion joints in bridges, pavements, railway tracks and pipes. Fitters use it to allow for the growth of long pipe runs, and DIY workers use it to leave gaps in decking, fences and flooring.

The same coefficient applies in every direction, so area grows by about twice the linear amount and volume by about three times. Different materials expand by different amounts, which is the basis of bimetallic strips in thermostats.

How the thermal expansion is worked out

Change in length = coefficient × original length × temperature change. The coefficient is the fraction by which the length changes per degree. A 10 m steel beam that warms by 50 °C grows by 6 mm. A 100 m aluminium pipe heated by 40 °C grows by 92 mm, more than 9 cm. PVC expands about four times as much as steel, 52 millionths per degree.

Every answer on this page comes from that one rule, so you can check any result by hand with a calculator. The figures shown underneath, such as other units, are conversions of the same answer.

• Eight materials plus custom
• Change in mm and percent
• Works in warming and cooling

Mistakes to avoid with thermal expansion

The values are typical; real alloys and plastics vary, and the coefficient itself changes slightly with temperature. For very large changes, check the manufacturer's data. A result that is negative means the length decreases because the final temperature is lower.

On phone and computer

On a phone, type into the boxes one after another and read the thermal expansion underneath; Copy result puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the thermal expansion move. The thermal expansion calculator works the same on both. Expansion depends on temperature change, so keep units right. Use the Temperature Converter for degrees, the Unit Converter for lengths, and the Density Calculator to see how a material changes.

Features

• Leave expansion gaps
• Plastics expand most
• Typical coefficients only
• Clear messages when the thermal expansion inputs make no sense
• Copy the result with one tap
• Private: nothing is uploaded

Frequently asked questions