Now that my career is settling in and my income is high enough I have decided to really double down on paying off my student loan debt.

I have 11 accounts over three sites, each account has a principle and an interest rate associated with it and I have X dollars to allocate every month across all 11 accounts.

I distinctly remember my engineering finance professor covering such a topic while I was in school and providing an example in Excel with the financial formulas to calculate the percent allocation to each account from the whole. But for the life of me can't remember the math/formula he used. The idea was to weight the individual accounts so that you payed the least principle and interest at the end of the run. His example was paying off loans for capital equipment but a loan is a loan, so the math should still fit.

Does anyone have any idea what Excel function I could apply to achieve this?

Thanks!