First of all you should measure your inseam length, because the body height alone is often too inaccurate to determine the frame size. For this you need a scale and a spirit level. If you do not have a spirit level, you can also use a large book.
Now take off your shoes and trousers - yes, the trousers too, because they can strongly influence the measurement result. If you have a spirit level, pull it up as horizontally as possible between your legs. It works the same with a book, but you should stand against a door or wall so that the upper side of your book is parallel to the floor. Now measure with the scale from the floor to the upper side of the spirit level or book. The value you have now determined is your so-called inseam length or inseam height.
Now you have to multiply this value by the factor 0.65 to get your frame size. With a inseam length of 80cm you need a frame with the size 52cm (80cm x 0.65=52cm).
If the calculated size is between two available frame sizes, you can apply the following rule.