Mortgage Planning
How to Use Mortgage Affordability Stress Tester
This friendly walkthrough shows the step-by-step flow: pick a region, enter price, down payment, term, income, debts, and costs, run the simulation, read DTI and default outputs, and save scenarios with clear labels.
Published: January 1, 2026 · Updated: January 1, 2026 · By FinToolSuite Editorial
Open the stress tester
Start a scenario, tweak inputs, and run a simulation in minutes with clear outputs.
Disclaimer
- Educational only, not financial, legal, or tax advice.
- Results depend on inputs and assumptions; no guarantees.
- Examples are illustrative and simplified.
Step-by-step setup
- Choose region preset: It sets starting tax, insurance, or PMI/LMI placeholders you can edit.
- Enter property price and down payment: This sets loan size and affects PMI/LMI if relevant.
- Choose term: Pick 15 or 30 years (or available options) to shape payment and interest exposure.
- Enter income and debts: Add gross income (and joint income if present) plus recurring debts for DTI.
- Fill monthly and advanced costs: Add property tax percent, PMI/LMI percent and threshold, HOA, maintenance, insurance placeholder, and closing cost assumptions.
- Run simulation: Run once the inputs look right; rerun after each change.
- Read outputs: Review recommended safe loan, DTI mid/high percentiles, and model default probability.
- Save scenarios: Label scenarios clearly (e.g., "Base 30yr" vs "Rate +1%"), then duplicate to compare.
- Export report: Use the export to capture a snapshot. Note the date, scenario label, and assumptions.
Common pitfalls
- Mixing monthly and annual numbers. Keep units consistent.
- Forgetting taxes or HOA. Add them before you compare scenarios.
- Relying on one run. Duplicate, change one variable, and rerun.
- Reading default probability as a forecast. It is model-based, not a guarantee.
Need a costs checklist? See what costs to include before you run more scenarios.
Outputs to read
Focus on direction and comparison, not precision. Keep the same assumptions when comparing two runs.
- Recommended safe loan: Model-based suggestion that can sit below lender maximums.
- DTI distribution: Check mid and higher percentiles to see stress tails. See DTI distribution explained.
- Default probability: Model output showing how often tough paths trigger stress. Not advice or approval.
Bottom line and next steps
Save a baseline, duplicate, change one input, and compare DTI tails, safe loan, and default probability direction. Rerun when assumptions change.
For detailed guidance on exports, visit report export help. To explore scenarios, read saving and comparing scenarios.
FAQs
How do I pick the right preset?
Choose the closest market preset, then adjust taxes, insurance, or PMI/LMI to your situation.
Should I round inputs?
Conservative rounding helps: round debts up, income down if uncertain, and stress costs.
Can I store multiple runs?
Yes. Save each scenario with a label and rerun after any change so exports match assumptions.
Where do I learn about stress testing?
How do I compare two prices?
Save a baseline, duplicate, change price only, and compare outputs. See scenario comparison.
How is my data handled?
See the Privacy Policy before exporting or sharing results.
Run a scenario now
Open the mortgage affordability stress tester, run a baseline, and save it before testing a second scenario.