Home loan calculator based on emi

I have recently purchased home for which I have already paid some ammount and rest we will be doing loan now our first draw of from loan ammount is 1600000 rs and total loan passed is 1.25 cr at interest rate of 8.5% for 15 years our emi is 1.23 lakh so I tried to calculate the interest ammount for this 16 lakh so that I can figure out how much ammount out of 1.23 lakh will go towards interest and how much towards principal ( ps we have just passed that ammount for the safer side we won't be taking that much ) also I will be adding another 1 lakh to principal as prepayment each month can anyone help figure this out thanks in advance