I had the very same problem, only in the opposite direction, living in Poland for the first 27 years of my life and moving to the UK just over a year ago.
Just bear in mind that 6ft is approximately 180 cm, anything above is above, and anything lower is lower. This gives you a first approximation with only remembering one number. Also, 4in is about 10cm and is easy to add/subtract both ways. This might not be very exact, but it will give you a quick idea.
Just bear in mind that 6ft is approximately 180 cm, anything above is above, and anything lower is lower. This gives you a first approximation with only remembering one number. Also, 4in is about 10cm and is easy to add/subtract both ways. This might not be very exact, but it will give you a quick idea.