HbA1c is a standardised test. In the US and many other countries they still report as percentage rather than mmol/mol.
HbA1c reflects your average glucose levels over about the last 3 months. There is a convertor to estimated average glucose levels here: http://www.diabetes.co.uk/hba1c-units-converter.html ( 7.2% is an estimated average of 8.9mmol/l)
The US and again many other countries use a different unit for measuring the immediate glucose in blood (ie as in a fasting glucose test or on a glucose meter). They use mg/dl rather than the mmol/l you will see in the UK.
to convert mg/dl - mmol/ l divide by 18 and multiply by 18 to change mmol/l to mg/dl
so 8.9mmol/l= 160mg/dl