Data overlap

I'm looking at a number of datasets which are all representative of the UK (there is little to no skew in each database - all representative of the UK adult population). Adult population in the country is 48m. The databases in order of size are:
19m
12m
4m
4m
4m
3m
1m
0.5m
0.5m

I'm trying to calculate the net number of records I'm likely to achieve by matching these datasets together. Clearly it will be larger than 19m. What excel formula can I use to create a estimation on the net number of records?