Draw an ellipse and choose any point P situated on it.
Write down the two basic formulas for calculating the eccentric anomaly. These are "cos E = x / a" and "sin E = y / b", where "x" and "y" are the coordinates of the point you chose in the previous step. "A" and "b" represent the semi-major and semi-minor axes of the ellipse respectively.
Compute one of the two values with a calculator. That is, compute "x/a" or "y/b." You may compute both to double-check your work in the next step.
Use the acos or asin function to calculate the eccentric anomaly E, depending on which value you computed in the previous step. If you calculated "x/a" in step 3, you will use the acos function. If you calculated "y/b" in step 3, you will use the asin function. You may calculate both to double-check your work.