Mortgage Stress Test
Run a mortgage stress test. See your payment at current rate +1%, +2%, +3% — and find the rate at which housing debt exceeds 38% of gross income.
Mortgage Stress Test
Enter your current mortgage and income details. The test shows what your monthly payment becomes if rates rise 1%, 2%, or 3% — and the break-point rate at which total housing debt exceeds your affordability threshold.
| Scenario | Rate | Monthly | Total DTI | Verdict |
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How to Use the Mortgage Stress Test
Enter your current mortgage
Balance, current rate, and years remaining come from your most recent mortgage statement. For ARM loans, use the current rate — not the start rate from when you took the loan.
Add household income and other debt
Gross monthly income before taxes — both spouses if you bought jointly. "Other debt" is the sum of monthly minimum payments on auto loans, student loans, credit cards, and any other consumer debt that lenders include in your DTI calculation.
Set your affordability ceiling
Fannie Mae's Selling Guide caps back-end DTI at 36% for manually underwritten loans, 45% with compensating factors and 50% through Desktop Underwriter; the CFPB's General QM definition carried a 43% cap until 2021, when it was replaced by a price-based test. 38% is a common conservative target that leaves room for emergencies. Canada's insured-mortgage limits (CMHC) are 39% gross and 44% total debt service. Set your own personal ceiling here.
Read the scenarios and the break-point
The table shows your monthly payment at +0%, +1%, +2%, +3%. Rows highlighted red exceed your threshold. The break-point card below shows the exact rate at which total housing debt crosses your ceiling — useful if you have an ARM coming up for reset.
Mortgage Stress Testing — Why Lenders Already Do This, and Why You Should Too
The Regulatory Background
After the 2008 mortgage crisis, US regulators codified the Ability-to-Repay (ATR) rule — 12 CFR 1026.43 — which requires lenders to make a good-faith determination that a borrower can repay the loan, including under reasonably foreseeable rate scenarios for adjustable-rate mortgages. The Qualified Mortgage (QM) standard layered on top originally set a 43% back-end debt-to-income ceiling; the CFPB's 2021 General QM rule (mandatory from 1 October 2022) replaced that cap with a price-based test — for most first liens the APR may not exceed the average prime offer rate by 2.25 percentage points or more — while still requiring lenders to consider and verify the borrower's DTI or residual income. Canada's Office of the Superintendent of Financial Institutions (OSFI) went further with Guideline B-20, which since January 2018 has required uninsured Canadian mortgages to qualify at a minimum qualifying rate — currently the greater of the contract rate plus 2 percentage points or a 5.25% floor — the federal stress test that has shaped Canadian housing affordability ever since.
The personal version of this exercise is exactly what the tool above runs: take your current mortgage, add scenarios at +1pp, +2pp, +3pp, and see whether the resulting monthly payment plus your other debt obligations breaches your personal affordability ceiling. For US borrowers with adjustable-rate mortgages (5/1, 7/1, 10/1 ARMs), this is the single most important question to ask each year — and especially in the 12 months before the first rate reset.
Back-End DTI: The Single Number That Decides Your Mortgage
The back-end debt-to-income ratio (DTI) is the percentage of your gross monthly income that goes to all monthly debt obligations — mortgage principal and interest, property taxes, homeowners insurance, HOA fees, plus auto loans, credit card minimums, student loans, and any installment debt. Fannie Mae's baseline is 36%, stretching to 45% with compensating factors and 50% through Desktop Underwriter; the old 43% QM cap no longer applies. The tool above uses back-end DTI as the threshold because it's the actual gatekeeper number — front-end (housing only) DTI is a softer constraint.
For a household earning USD 100,000 per year (USD 8,333/month gross), a 38% DTI ceiling means total monthly debt service can't exceed USD 3,167. If auto and student loans already take USD 600, your maximum monthly mortgage payment is USD 2,567. At 6.5% on a 30-year loan, that supports a USD 405,000 mortgage. At 8.0%, only USD 350,000. The 1.5pp rate movement is worth USD 55,000 of buying power.
"A 2pp rise on a USD 320,000 / 27-year mortgage at 5.5% adds roughly USD 410 to the monthly payment — nearly five percentage points of DTI on a USD 8,500 gross monthly income."
When to Run This Test on Yourself
Three triggers should make you run a personal stress test: (1) you have an ARM with a reset coming in the next 12-24 months — the stress test tells you what you're walking into; (2) you're considering refinancing into an ARM to get a lower starter rate — the test tells you the worst-case payment after reset; (3) you bought near the top of your DTI in a low-rate environment and rates have moved against you — the test tells you how much headroom you have if your income drops or your other debt rises.
The other use case is buying. Lenders qualify you at today's rate, but you'll have to live with the payment if rates rise during the life of the loan. Self-stress-testing at +2pp gives you a buffer beyond what the lender's QM minimum ensures. Conservative borrowers buy a house where the +2pp scenario still fits inside 36% DTI; aggressive borrowers run up to the 45–50% agency ceilings at today's rate and accept the risk of needing to refinance or sell if rates move further.
Canada qualifies you two points above the rate you will pay
The Ability-to-Repay (ATR) rule (12 CFR 1026.43) is the federal requirement that US lenders prove a borrower can repay — including under foreseeable rate scenarios.
The General Qualified Mortgage definition capped back-end DTI at 43% from 2014 to 2021; the CFPB's 2021 rule replaced the cap with a price test (APR within 2.25pp of the average prime offer rate).
Canada's OSFI Guideline B-20 requires uninsured mortgages to qualify at the greater of the contract rate +2pp or a 5.25% floor — a test that has shaped Canadian housing affordability since 2018.
The Bank of England's Financial Policy Committee required UK lenders from 2014 to test each borrower at 3pp above the reversion rate; it withdrew that test on 1 August 2022 but kept the cap on lending above 4.5× income.
For a USD 300,000 / 30-year loan starting at 5–7%, a 1 percentage point rate rise adds roughly USD 190–205 a month — and USD 68,000–74,000 of interest over the term.
A 5/1 ARM is fixed for five years, then adjusts annually; its note states the caps — commonly 2pp per adjustment and 5pp over the life of the loan, but read yours.
Fannie Mae's Selling Guide (B3-6-02) sets back-end DTI at 36% for manual underwriting, 45% with the credit-score and reserve conditions in its Eligibility Matrix, and 50% for loans run through Desktop Underwriter.
Canada's insured mortgages (CMHC) are capped at 39% gross debt service and 44% total debt service — both computed at the stress-test rate, not the contract rate.
EU mortgage rules under Directive 2014/17/EU (Article 18) require a thorough creditworthiness assessment before lending, but set no EU-wide debt-to-income ceiling — each member state calibrates its own.
The 2008 mortgage crisis in the US was driven partly by stated-income loans where ATR was effectively absent — the rule explicitly responds to that experience.
Frequently Asked Questions
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A mortgage stress test models what your monthly payment becomes if interest rates rise. It answers the question "could I still afford my mortgage if rates were 2 percentage points higher?" Lenders run formal stress tests during underwriting under regulations like the US Ability-to-Repay rule and Canada's OSFI B-20. The personal version is the same exercise: apply scenarios of +1pp, +2pp, +3pp to your current rate, check whether the new monthly payment plus your other debt still fits inside your personal affordability threshold (36–45% of gross monthly income under US agency guidelines).
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Back-end debt-to-income (DTI) is the percentage of your gross monthly income that goes to all monthly debt obligations — mortgage payment, property taxes, homeowners insurance, HOA fees, auto loans, credit card minimums, student loans, and any other recurring debt service. Fannie Mae's Selling Guide caps it at 36% for manually underwritten loans, 45% with compensating factors and 50% through Desktop Underwriter; the CFPB's former 43% QM cap was replaced by a price-based test in 2021. It matters because it is one of the ratios lenders weight most heavily — and the higher it sits, the smaller the income drop or expense spike it takes to push you into delinquency.
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These are calibrated to typical ARM reset caps and observed historical rate moves. Most US adjustable-rate mortgages cap the annual adjustment at 2 percentage points and the lifetime adjustment at 5 percentage points. Freddie Mac's PMMS 30-year rate moved from about 2.7% (January 2021) to about 7.8% (October 2023) — a 5-percentage-point swing in under three years. Testing +1pp, +2pp, +3pp covers the realistic short-term stress for a fixed-rate borrower and the typical first-reset stress for an ARM borrower. Canada's OSFI B-20 stress rate is the greater of contract +2pp or 5.25%, which at current rates is the +2pp row on this tool.
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Enter your current loan balance, the current note rate (the one you're paying today, not the start rate from origination), and the years remaining. The tool's +1, +2, +3 scenarios will show what monthly payment you face if you reset at +1pp / +2pp / +3pp. Your loan note specifies the reset index (typically the Secured Overnight Financing Rate or SOFR, or the older one-year Treasury), the margin (commonly 2.25–2.75pp), and the periodic + lifetime caps. Compare today's index value to the index value when you signed — that delta plus the margin is approximately your new rate. If the worst case fails the affordability test, refinance into a fixed-rate product before the reset.
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This tool models principal and interest only — the PI portion of PITI. To capture the full housing payment, add your monthly property taxes (1/12 of annual), homeowners insurance, and HOA into the "Other monthly debt" field, or reduce your affordability threshold accordingly. A more conservative version: subtract estimated annual property taxes + insurance from gross income before computing DTI. For US borrowers, effective property-tax rates ran from 0.27% (Hawaii) to 2.23% (New Jersey) of home value in 2023 per the Tax Foundation — roughly USD 110–930 a month on a USD 500,000 home.
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Front-end DTI is just housing (mortgage PITI ÷ gross income); back-end DTI adds all other recurring debt. The traditional US underwriting rule is front-end ≤ 28% and back-end ≤ 36%; Fannie Mae's back-end ceiling stretches to 45% with compensating factors and 50% through Desktop Underwriter. This tool uses back-end as the threshold because it's the actual gating ratio — front-end can be met but back-end fail if other consumer debt is high.
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Canada's Office of the Superintendent of Financial Institutions Guideline B-20 requires uninsured Canadian mortgage borrowers to qualify at a minimum qualifying rate that OSFI sets and reviews at least annually — currently the greater of (a) the contract rate + 2 percentage points or (b) a 5.25% floor. Introduced January 2018, B-20 has materially shaped Canadian housing affordability — it's why a Canadian household offered 4.5% must qualify their budget as if rates were 6.5%. Since November 2024 a straight switch of lender at renewal (same balance, same amortisation) is exempt. The US has no direct equivalent.
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Three options: (1) reduce other debt — pay off the auto loan or credit card balances; even USD 200/month off other debt service moves the headroom; (2) extend the mortgage term — going from 27 years left to a fresh 30-year refinance lowers the monthly payment, but at the cost of much more lifetime interest; (3) increase income — refinances qualify off the higher household income if a spouse returns to work or you get a promotion. The order to try is usually 1 → 2 → 3 because debt paydown is the only one that improves your finances rather than rearranging them.
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Singapore has a fully codified regime: the Mortgage Servicing Ratio (MSR) caps payments on HDB flats and new ECs at 30% of gross monthly income; the Total Debt Servicing Ratio (TDSR) caps total monthly debt at 55%. Both are MAS rules, and for a loan from a bank or finance company they are computed at the higher of a 4% medium-term floor or the loan's thereafter rate — so a Singapore loan is stress-tested at origination the way this tool does it. An HDB concessionary loan is assessed by HDB instead, against its own 3% floor; that is not a MAS rule, and it does not change the 2.6% HDB actually charges. Malaysia leaves the debt-service-ratio ceiling to each bank's policy under Bank Negara's responsible-financing guidelines, and Indonesia, the Philippines and Vietnam rely on bank-level thresholds rather than a published national cap. If you have an SG/MY loan, the right tool is our Mortgage Calculator with its TDSR-aware logic.
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Use 36% back-end DTI rather than the 38% default. Two reasons specific to expats: (1) your US emergency cushion is usually smaller — you don't yet have the network, family backstop, or local credit lines you'd have at home; (2) currency-flow risk if part of your income or savings is in SGD/MYR — a USD strengthening cycle can pressure your USD-denominated mortgage in ways a US-born borrower doesn't face. The 36% ceiling gives you 7-9% of pre-tax income as a buffer. Conservative ASEAN expats with single-income households should consider 32-34%.
Method & sources
How it computes
Computes the level P&I payment at the current rate and at +1, +2 and +3 percentage points, adds other monthly debt, and divides by gross monthly income to give back-end DTI; the break-point rate at which DTI meets the chosen ceiling is found by bisection on the payment formula. P&I only — taxes and insurance are not modelled.
What this tool implements
- Level-payment amortisation M = P·r(1+r)^n/((1+r)^n−1), monthly compounding; scenarios at +1/+2/+3pp on the note rate
- Back-end DTI ceilings offered as presets: 36% (Fannie Mae Selling Guide B3-6-02 manual-underwriting maximum), 38% (conservative middle), 43% (the General QM cap in force 2014–2021, superseded by the CFPB's price-based test effective 1 Mar 2021 / mandatory 1 Oct 2022)
- Canada's OSFI B-20 minimum qualifying rate (greater of contract + 2pp or 5.25%) and CMHC 39% GDS / 44% TDS cited as comparators; the tool's +2pp row is the B-20 test at current rates
- Currency selector changes display only; the arithmetic is jurisdiction-neutral
Sources
What can make this go out of date
- Fannie Mae Selling Guide B3-6-02 DTI maxima (36/45/50) — revised with Selling Guide updates, last 02 Apr 2025
- OSFI minimum qualifying rate (buffer and floor) — reviewed at least annually by OSFI, currently contract + 2% or 5.25%
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