How Our DSCR Calculator Works
This page explains exactly how the DSCR Formulas calculator produces its numbers, what assumptions it makes, and why a lender's final DSCR may differ from the estimate shown here. Treat every result as an educational estimate, not a lending decision.
The Formula (Residential Default)
DSCR = Gross Monthly Rent ÷ Monthly PITIA
For most 1–4 unit residential DSCR loan programs, lenders commonly underwrite gross monthly rent divided by monthly PITIA (principal, interest, taxes, insurance, and association dues). That is the default mode on this site's calculator.
Framing sources (educational; reviewed mid-2026): Lineage — How to Calculate DSCR; Lendmire — How Rental Income Is Calculated; Mbanc — DSCR Loans Guide. Program matrices still control.
Optional Analysis Formula
DSCR = NOI ÷ Annual Debt Service (P&I)
Commercial real estate and textbook analysis often use NOI ÷ annual P&I debt service. The calculator's Analysis mode shows this for investment context. It is usually not the same ratio a residential DSCR lender will use.
How the Calculator Computes Each Input
| Input | How it is used |
|---|---|
| Purchase price | Down-payment percentage is applied to calculate the loan amount. |
| Down payment % | Converted to a dollar amount and subtracted from the purchase price. |
| Interest rate | Annual rate converted to a monthly rate for the amortization formula. |
| Loan term | Total number of monthly payments used to calculate P&I. |
| Gross monthly rent | Numerator for residential DSCR (Rent ÷ PITIA). Also annualized for NOI/cash-flow outputs. |
| Vacancy rate | Used for NOI / cash-flow analysis only — not subtracted inside residential Rent ÷ PITIA. |
| Property tax, insurance, HOA | Included in PITIA (residential DSCR denominator) and in operating expenses for NOI. |
| Property management & maintenance | Included in NOI / cash-flow only — typically not inside lender PITIA DSCR. |
What Is Included in Residential PITIA DSCR
- Gross monthly rent (as entered; lenders may use the lesser of lease vs appraisal market rent)
- Divided by monthly PITIA: P&I + property tax + insurance + HOA/association dues
What Is Excluded from Residential Lender DSCR (Usually)
- Vacancy allowance
- Property management and routine maintenance (cash-flow items)
- Capital expenditures, depreciation, income tax
- Reserves and liquidity overlays (eligibility items, not the ratio itself)
Why a Lender's DSCR May Differ
Every lender applies its own underwriting overlays. Common differences include:
- Rent source: lesser of lease vs Form 1007 / market rent is common.
- STR haircuts: short-term rental income may be reduced or ignored.
- Taxes/insurance: post-purchase tax estimates and landlord policies can differ from what you typed.
- Interest-only: some programs use ITIA instead of PITIA during an IO period.
- Formula convention: ask whether the quote is Rent ÷ PITIA or NOI-based.
Calculator Limitations
This tool runs entirely in your browser. We do not store your inputs. Outputs are mathematical estimates based on your inputs. They do not guarantee that any lender will approve your loan, offer a quoted rate, or use the same assumptions.
Worked Example (Matches Homepage Defaults)
Same scenario as the calculator defaults: $300,000 purchase, 25% down ($75,000), $225,000 loan at 7.25% for 30 years, $2,800 gross monthly rent, property tax $250/mo, insurance $125/mo, HOA $0. Vacancy 7%, management $280, maintenance $140 appear in NOI/cash-flow outputs but not in residential DSCR.
- Monthly P&I ≈ $1,534
- Monthly PITIA = $1,534 + $250 + $125 + $0 ≈ $1,909
- Residential DSCR = $2,800 ÷ $1,909 ≈ 1.47
- Effective gross income = $2,800 × 12 × (1 − 0.07) = $31,248
- Annual opex (tax+ins+HOA+mgmt+maint) = ($250+$125+$0+$280+$140) × 12 = $9,540
- NOI = $21,708
- Analysis DSCR = $21,708 ÷ ($1,534 × 12) ≈ 1.18
The two ratios differ on purpose. Use residential Rent ÷ PITIA to estimate lender-style coverage; use Analysis NOI mode for investment cash-flow context. A real lender may still arrive at a different number after overlays.