Floating Rate Debt Service Calculator

Floating-rate debt service swings with the index. This calculator projects monthly payments across three rate paths.

Balance

Current index %

Spread (bps)

Low scenario index %

High scenario index %

Base monthly DS

$59,167

Low monthly DS

$55,000

High monthly DS

$71,667

How the math works

Monthly DS = balance × (index + spread) ÷ 12 for each scenario. Interest-only; add amortization if applicable.

Bracket scenarios give planning range. Typical range is 15-30% between low and high. Reserve at high-scenario levels, operate at base, and retain surplus when actual tracks low.

How to Use

Enter balance.
Enter current index rate.
Enter spread.
Enter low and high scenario indexes.
Read debt service range.

Frequently Asked Questions

Rate path scenarios?

Low: current − 50 bps. Base: current + 25 bps. High: current + 150 bps. These span typical 12-month scenarios in moderately volatile markets.

Floors and ceilings?

Floor prevents rate dropping below a level (protects lender). Ceiling (cap) limits rate upside (protects borrower). Model both into each scenario's debt service.

Budget buffer?

Reserve 3-6 months of high-scenario debt service. Separate from base operating reserves. Reimburse from cash flow once rate scenario resolves.

How does this interact with the rest of the capital stack?

Each tier of the stack affects the next. Senior debt constrains LTC and DSCR. Mezz and pref consume equity spread. Interest rate hedges protect DSCR but cost premium. Always model the full stack holistically — optimizing one tier alone often degrades another. Institutional underwriters run three or four scenarios across the stack before committing capital.