According to the definition, stroke volume is the difference in the “full ventricle” and the “empty ventricle”. This relationship can be expressed mathematically as follows:

Stroke volume = EDV (mL) - ESV (mL)

If EDV is 130mL of blood and ESV is 60mL of blood the calculation is:

Stroke volume = 130 mL - 60 mL = 70 mL/beat
Amount spent = amount at start – amount left over

Perhaps it may be easier to use money as an example for this math. Calculating ejection fraction is no different than describing how much of your money you spend at the grocery store. For example, if you start with $130 and buy groceries for $70, you still have $60 left over. Additionally, since you started with $130, the most you could have spent would have been $130. You can turn this into a fraction $70 spent out of $130, and write it as 70/130, which is just more than one-half. Some people like to use percentages and would say that they spend 54% of their budget, shown below. However, you should be able to show mathematically that you got to this conclusion by the following equation:

% of money spent = $ at start - $ you still have x 100%
                                             $ at start

If you substitute actual cardiovascular number here you get:

EDV = blood at the end of diastole (same as beginning of contraction and $ at start above)
ESV = blood at the end of systole (same as $ you still have above)

Ejection fraction = EDV – ESV x 100%                       
                                    EDV                                        

Further substituting SV for EDV minus ESV gives the equation:

Ejection fraction = SV x 100%       
                              EDV

Therefore, going back to the original equation you get: