The past 12 months have been a life changing period for Kate who gave birth to Prince George in the summer.
Her baby son will one day be king and he was christened in front of the Queen, Prince of Wales and other members of his immediate family in October.
As a mother of a five-month-old baby it is unlikely the Duchess will be celebrating into the small hours.
But a romantic birthday meal at home could be on the cards for Kate who was born at the Royal Berkshire Hospital in Reading, on January 9 1982.
Kate and husband William recently moved into their Kensington Palace apartment and an intimate dinner could be held at the picturesque royal residence.
A Kensington Palace spokesman said that Kate would be spending her birthday "privately".
The couple were university sweethearts who met at St Andrews University in Scotland before marrying in April 2011.
William began an agricultural management course at Cambridge University on Monday and may spend much of Kate's birthday studying at the famous university.
The Duke is commuting a number of days a week to attend the course run by the Cambridge Programme for Sustainability Leadership.