How to estimate the size of a delete statement?

Good morning,

I'd like to know if there are any ways to estimate the size of a table after a delete statement.

Let's say I have a table table_A with 1000000 rows and sized 10Gb (info retrieved from sp_spaceused table_A)

I know I'm going to delete 350000 rows and I'd like to estimate the size of my final table, how can I proceed?

Can I just do a mathematical rule to estimate the size?

Should I use optdiag ouput to know the size of a row and 'x' by number of rows?

Thanks

Simon