For this example, we want to calculate cumulative principal payments over the full term of a 5-year loan of $5,000 with an interest rate of 4.5%. To do this, we set up CUMPRINC like this:
rate - The interest rate per period. We divide the value in C6 by 12 since 4.5% represents annual interest:
nper - the total number of payment periods for the loan, 60, from cell C8.
pv - The present value, or total value of all payments now, 5000, from cell C5.
start_period - the first period of interest, 1 in this case, since we are calculating principal across the entire loan term.
end_period - the last period of interest, 60 in this case for the full loan term.
With these inputs, the CUMPRINC function returns 5,000, which matches the original loan value as expected.