Thermal Expansion Calculator
Find how much a material expands when heated.
Steel ≈ 0.000012, aluminium ≈ 0.000023.
Results update as you type.
How it works
Most materials grow when heated and shrink when cooled, and this thermal expansion calculator finds exactly how much a solid changes length from its original length, its expansion coefficient, and the temperature change. It reports both the change in length and the resulting new length, so you can see the effect of a temperature swing at a glance. This subtle stretching is why bridges have expansion joints, why railway tracks can buckle in a heatwave, and why a stuck metal lid loosens under hot water. Accounting for expansion matters in almost every branch of engineering. Pipes, power lines, and long spans must be designed with room to move, and precision instruments must compensate so that a warm afternoon does not throw off their readings. Because the change depends on the material, the tool uses a coefficient specific to each substance, letting you compare how steel, aluminium, or glass respond to the same heating. The formula works because each degree of temperature change stretches the material by a fixed fraction of its length, set by the coefficient, so longer objects and larger temperature swings both produce proportionally bigger movements. Engineers, machinists, and physics students rely on a thermal expansion calculator to predict clearances, avoid damaging stress, and understand how everyday structures cope with the changing seasons.
ΔL = coefficient × original length × temperature change
Linear thermal expansion multiplies the coefficient of expansion by the original length and by the temperature change, because each degree stretches the material by a fixed fraction of its length set by that coefficient. Longer objects therefore move more, and larger temperature swings move them further. Adding this change to the original length gives the new length. The relationship stays accurate as long as the temperature change is moderate and the material behaves uniformly.
Source:Standard physics (thermal expansion)
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter original length, expansion coefficient and temperature change.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Change in length updates instantly as you type — no button to press.
Frequently asked questions
What units should I use?
Enter the original length in metres, the temperature change in degrees Celsius or kelvin, and the coefficient in units of per degree Celsius, which is how expansion coefficients are normally tabulated. The change in length and the new length then come out in metres. Because a Celsius degree and a kelvin are the same size, you can use either scale for the temperature change without affecting the result.
Where do I find the expansion coefficient?
Coefficients of linear thermal expansion are published in engineering handbooks and material datasheets for every common substance. Typical values are around 0.000012 per degree Celsius for steel, 0.000023 for aluminium, and 0.000009 for glass. Look up the figure for your specific material and enter it directly. Using an accurate, material-specific coefficient is essential, since even small differences noticeably change the predicted expansion over long lengths.
Why do materials expand when heated?
Heating a material makes its atoms vibrate more vigorously, so on average they push slightly further apart, and the whole object grows. Cooling reverses this, drawing the atoms closer and shrinking the material. The expansion coefficient captures how strongly a particular substance responds, since the strength of its atomic bonds sets how far the atoms move for each degree of temperature change applied to it.
Does this handle contraction when cooling?
Yes. Enter a negative temperature change to model cooling, and the calculator returns a negative expansion, meaning the material contracts, along with a new length shorter than the original. The same formula covers both directions, because heating and cooling are simply positive and negative temperature changes. This makes the tool useful for predicting how components shrink in cold conditions as well as how they grow in the heat.
What is the difference between linear and volumetric expansion?
This calculator handles linear expansion, the change in a single length or dimension. Volumetric expansion describes how an object's whole volume grows, and for a solid its coefficient is roughly three times the linear one, since expansion happens along all three dimensions at once. Use linear expansion for rods, pipes, and rails, and volumetric expansion when you care about the total space a heated body occupies.