There is majority support in parliament and across the United Kingdom to implement a "smoke-free generation" policy which would mean people born on or after January 1, 2009, could never legally be sold tobacco. To explore the potential impact this policy could have, we estimated the number of young adults (18-25 years) currently taking up smoking each year by area across the United Kingdom. Using data from the Office for National Statistics (ONS), Annual Population Survey (APS), and Smoking Toolkit Study (STS), we estimated the total number of 18- to 25-year-olds taking up smoking each year, based on national estimates of population size (ONS) and the proportion who reported ever having regularly smoked (STS). We used local data on adult smoking rates (APS) to apportion the national estimated number of young adults taking up smoking to specific areas. Around 127500 18- to 25-year-olds in the United Kingdom start smoking regularly each year (~350 each day); 105700 each year in England, 11500 in Scotland, 6500 in Wales, and 3800 in Northern Ireland. Uptake estimates varied across localities: for example, North East Lincolnshire had the highest proportion of young adults taking up smoking each year (3.9%) and Wokingham had the lowest (0.9%). Despite reductions in smoking prevalence over recent decades, hundreds of young adults in the United Kingdom start smoking every day. Data on rates of uptake among individual local authorities can be used to focus attention locally prior to the introduction of new age of sale laws.