A tensometer is a device used to evaluate the Young's modulus (how much it stretches under strain) of a material. In Solid mechanics, Young's modulus (E is a measure of the Stiffness of an isotropic elastic material The tensometer is usually loaded with a sample between two grips that are adjusted manually to apply force to the specimen. In Physics, a force is whatever can cause an object with Mass to Accelerate. The measurements taken are force and extension and a tensometer gives directly the load extension curve and not the stress strain curve. A tensometer can be either electronic or manual, the latter being operated by a handle to apply the force.

It is possible to use a tensometer to test a material to its breaking point. The results gained from a tensometer are commonly used to plot stress-strain curves for materials that enable them to be compared without the confusion of sample dimensions.