Concrete Thermal Expansion Calculator
Estimate the free linear expansion or contraction of a concrete member from its length, coefficient of thermal expansion and temperature change. The result includes movement and thermal strain so you can see the scale of the effect.
Calculate thermal movement
Thermal movement result
The thermal expansion formula
Linear thermal movement is commonly estimated from the product of the member length, coefficient of linear thermal thermal expansion and temperature change.
The coefficient should be expressed on the same temperature basis as the temperature change used in the calculation.
Worked example
For a 30 m member, α = 10 × 10⁻⁶/°C and a 30°C rise:
This is a free-movement estimate. A restrained member may not move the full 9 mm; instead, the restraint can create stress.
The coefficient depends on the concrete
The coefficient of thermal expansion is influenced by concrete composition, especially aggregate type, moisture and temperature range. For important engineering work, use a coefficient appropriate to the actual materials rather than treating one number as universal.
Temperature movement versus cracking
Thermal movement alone does not predict cracking. Restrained shrinkage, thermal gradients, creep, reinforcement, geometry, joints and construction sequence can all change the stress state.
A useful engineering workflow is to calculate free movement first, then evaluate whether the structural or pavement system can accommodate it.
Expansion joints and movement joints
The existence and spacing of joints depends on the structure or pavement system and applicable design practice. This calculator should not be used to select joint spacing by itself.
Common mistakes
Using a coefficient per °F with °C change: keep the temperature basis consistent.
Forgetting direction: cooling produces contraction.
Assuming full movement occurs: restraint changes behavior.
Calling movement a crack prediction: movement and stress are different engineering quantities.
Limitations
This is a one-dimensional free-movement estimate. It does not model restraint, stress, creep, shrinkage, thermal gradients, joint behavior or structural cracking.
Frequently Asked Questions
What is the concrete thermal expansion formula?
ΔL = α × L × ΔT.
What coefficient should I use?
Use material- and project-appropriate data whenever possible.
Does concrete contract when it cools?
Generally yes, for free thermal movement.
Does this predict cracking?
No. Cracking requires a stress/constraint assessment.
Can I use feet and inches?
Yes. The calculator converts the entered length to a consistent basis.