Mortgage & Home Buying Calculators
Buying a home is the biggest financial decision most people make. These calculators walk you through the process — from figuring out how much you can afford to comparing refinance options years later. Work through them in order for a complete picture.
Guide maintained by Ahmet Ozdemir. Numbarn reviews calculator formulas against reference cases and edits explanatory copy for clarity and limitations. We do not claim third-party professional certification on every page. Last expanded July 2026.
How to use this guide
- Cap the search with affordability using income, debts, and a stress-tested rate—not the listing price you hope for.
- Model down payment vs PMI tradeoffs, then estimate full monthly housing cost (P&I plus tax, insurance, HOA).
- Open the amortization schedule to see interest share in year one versus later years.
- Run rent vs buy for your expected hold period, including selling costs and down-payment opportunity cost.
- Only then compare refinance or payoff extras—optimization after the buy decision, not instead of it.
- 1
House Affordability
Start here: how much home can you afford based on income and debts?
- 2
Down Payment
See how different down payments affect your loan and whether you'll need PMI.
- 3
Mortgage Payment
Estimate monthly P&I, property tax, insurance, PMI, and HOA with an amortization schedule.
- 4
Amortization Schedule
See exactly how each payment splits between principal and interest over the life of the loan.
- 5
Refinance Comparison
Compare your current loan to a new one: monthly savings, break-even, and lifetime interest saved.
- 6
Rent vs Buy
Is it cheaper to rent or buy in your situation? Compare total cost over time.
- 7
Mortgage Payoff
See how extra payments shorten your loan and reduce total interest.
Example scenarios
First-time buyer with 10% down
Affordability → down payment (PMI on) → mortgage payment with tax/insurance/PMI/HOA extras included → rent vs buy at a 7-year horizon. If the conservative rate case breaks the budget, shrink price before shopping harder neighborhoods.
Move-up buyer with equity
Estimate net proceeds after selling costs, then re-run affordability on the next purchase. Compare a 15- vs 30-year term on total interest, not only payment.
Common mistakes to avoid
- Skipping total housing cost (tax, insurance, HOA, maintenance) and focusing only on principal + interest.
- Comparing loans by monthly payment only instead of total interest and break-even horizon.
- Using one market-rate assumption without checking best/worst-case scenarios.
Decision checklist
- Do I still have 3–6 months of cash reserves after closing?
- Does the payment stay affordable if rates or insurance jump 1%?
- Have I compared total interest, not only the monthly number?
Frequently asked questions
Which home-buying calculator should I start with?+
Start with affordability, then down payment, then mortgage payment. After that use amortization/refinance for optimization.
Should I compare rent vs buy before pre-approval?+
Yes. Rent-vs-buy helps set strategy while pre-approval confirms realistic borrowing limits and lender terms.
What to do next
- Save at least two scenarios while testing assumptions.
- Compare scenarios in /saved/compare before deciding.
- Use source links and category disclaimers for final verification steps.