Is there a way to calculate thrust without running experiments?
For the case of an electric motor driving a propeller, you can get a rough approximation for the thrust t from the power p consumed by the motor when the plane is flying with a constant velocity v, since $p = t \times v$. Of course, you should use coherent units, as newtons, m/s and watts, and include a large correction factor, as the real efficiency will be very far from 100%...

For the stationary case, in Wikipedia (entry 'disk loading') you can find an expression for the stationary case, derived from momentum considerations.