Instantaneous acceleration is defined as the rate of change of velocity over time. To calculate it, one must take the derivative of the velocity function rather than simply subtracting two velocity values. The formula a = (v - vo) / t can be used, where 'a' is acceleration, 'v' is final velocity, 'vo' is initial velocity, and 't' is time. Understanding this concept is essential, even for those not studying calculus-based physics. Properly applying these principles will lead to accurate calculations of instantaneous acceleration.