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dscr-ratio

Debt service coverage ratio (DSCR) — the single number that decides most rental-property loans. DSCR = net operating income ÷ annual debt service.

dscr-ratio is a pure-Rust, zero-dependency crate that computes DSCR, the amortizing monthly payment behind it, and a plain-language lender verdict. It is the math behind the DSCRRadar DSCR loan calculator, a free tool for sizing real-estate investment loans.

Why DSCR matters

For investment-property and rental loans, lenders underwrite on the property's cash flow, not the borrower's personal income. DSCR is the headline ratio:

DSCR Verdict What it means
< 1.00 fail Rent does not cover debt service; most lenders decline.
1.00–1.15 marginal Barely covers debt; few programs, worse terms.
1.15–1.25 tight Meets minimums; pricing improves above this band.
1.25–1.35 good Standard "best terms" threshold for DSCR lenders.
≥ 1.35 strong Comfortable cushion; best pricing and LTV.

A DSCR ≥ 1.25 is typically where DSCR lenders price their best terms; below 1.00 the property does not cover its own loan from rent.

Install

[dependencies]
dscr-ratio = "0.1"

Quick start

use dscr_ratio::{monthly_payment, annual_debt_service, dscr, verdict};

// $100k loan, 7%, 30 years
let monthly = monthly_payment(100_000.0, 0.07, 360);   // ≈ 665.30
let debt    = annual_debt_service(monthly);            // ≈ 7,983.61
let ratio   = dscr(24_000.0, debt);                    // NOI / debt
println!("{}", verdict(ratio));                        // "good"

Run a full deal interactively

The crate handles the core math; for NOI line-items, reserves, and multiple scenarios use the DSCRRadar DSCR loan calculator.

Features

  • Pure Rust, no deps — f64 arithmetic, #![no_std]-friendly style.
  • DSCR — noi / annual_debt_service, safe against non-positive debt.
  • Amortizing payment — standard fixed-rate mortgage formula.
  • Lender verdict — bucketed against common DSCR thresholds.
  • MIT licensed — embed anywhere.