This link makes working it out easy - just type in the two numbers . (In the boxes about half way down the page) and it tells you....
nhs.uk/conditions/high-bloo...
Now i have my new monitor which takes 3 readings and gives you the average (my GP insists on getting an average) at the press of the button and this link I now no longer have to practice the 3 times table and short division for a week before each appointment......