I saw some people on Searchfunder ask about DSCRs so I made a free tool that calculates DSCR based on acquisition price and loan amount: https://godealwise.com/blog/debt-service-ratio-calculator-for-sba-loans

You can go through it multiple times to see how exit multiple, seller financing, loan rates and loan terms affect the DSCR.

As a bonus, it also calculates the SBA guarantee fee which is charged to lenders but usually passed on to you. The SBA has a progressive fee schedule based on loan amount so calculating it manually isn't straightforward.