Finance category
Mortgage, loan, investing, tax, and money calculators.
Loan Constant Calculator
Loan constant combines rate and amort. This calculator computes.
Loan constant %
8.4814%
Monthly payment factor
0.007068
Annual debt service / $1 loan
$0
How the math works
Monthly factor = r/12 / (1 − (1+r/12)^−months). Annual = monthly × 12. Constant = annual × 100.
7% 25-year loan: 8.48% constant. Quick DSCR at $500k NOI / $5M loan: 500k / (5M × 8.48%) = 1.18x. Accretive to 8%+ cap rate; dilutive below 8%.
How to Use
- Enter rate %.
- Enter amortization years.
- Read loan constant %.
Frequently Asked Questions
What's loan constant?
Annual debt service / original loan amount. Combines interest rate and amortization into single metric. E.g., 6% 30-year loan: constant ~7.19%. Used to calculate DSCR, spread analysis, proceeds sizing — simpler than carrying P&I separately.
Why matter?
Quick DSCR calc: NOI / (loan × constant). Quick sizing: loan = NOI / (DSCR × constant). Spread analysis: cap rate − loan constant = positive if accretive, negative if dilutive. Shortcut math used throughout real estate finance.
Interest-only special?
IO loan constant = rate (no amortization). 6% IO: constant 6%. Coverage math easier but exit strategy risk higher (balloon). 25-year amort: constant = rate + amortization contribution. 30-year: slightly less. Match amort to hold strategy.
How often should I rerun this?
Rerun this calculator whenever inputs change materially — new rent roll data, rate moves, loan balance updates, or quarterly operating data. For active deals, monthly refresh is typical. For stabilized assets under monitoring, quarterly is fine. Treat the output as a decision tool, not a one-time answer — market conditions evolve and so should your analysis.
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Size loan coverage as NOI ÷ annual debt service — the general-purpose ratio banks and DSCR-style underwriting rely on.