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⚙ Interactive calculator — use inputs above to calculate instantly.
The conventional wisdom is 20% down to avoid Private Mortgage Insurance (PMI). But putting down less is often financially smarter — especially in appreciating markets. This calculator shows the true cost of different down payment amounts including PMI, opportunity cost, and time to save.
| Down Payment | On $400K Home | Monthly PMI | Total PMI Cost |
|---|---|---|---|
| 3% (FHA min) | $12,000 | $167-250/mo | $30K+ (life of loan) |
| 5% conventional | $20,000 | $133-200/mo | $24K until 20% equity |
| 10% | $40,000 | $67-100/mo | $12K until 20% equity |
| 20% | $80,000 | $0 | $0 |
If home prices are rising 5-8%/year in your market, waiting to save from 10% to 20% down costs you appreciation on the full home value. In a $400,000 market rising 7%/year, every year you wait costs $28,000 in appreciation — far more than the $2,400/year PMI. Many financial planners now recommend 10% down and investing the remaining capital at market returns.
PMI automatically terminates when your loan reaches 78% LTV (based on original purchase price per the Homeowners Protection Act). You can request removal at 80% LTV. FHA MIP (mortgage insurance premium) is different — it remains for the life of the loan if you put less than 10% down. This is why conventional loans often beat FHA for buyers who can afford 5-10% down.
Use this calculator as a starting point, not a final answer. Run three scenarios: pessimistic (lower returns, higher costs, worst-case tax rates), base case (your expected scenario), and optimistic (favorable conditions). The range between these three scenarios tells you how much uncertainty surrounds your plan and how much buffer you need.
Once you have your numbers, cross-reference them with complementary calculators. A mortgage payment should be checked against your overall budget and DTI ratio. A retirement projection should account for Social Security income, potential pension, and healthcare costs in retirement. Tax calculations should be checked against available deductions and credits you may qualify for. No single calculator captures everything.
Where you hold investments matters as much as what you hold. High-growth assets belong in Roth accounts where growth is tax-free. Income-producing assets like bonds belong in traditional 401(k) or IRA where taxes are deferred. Tax-managed index funds belong in taxable brokerage where you can harvest losses. This asset location strategy adds 0.2-0.4% annually to after-tax returns without changing your investments at all.
The lifetime value of proper tax planning for a median American household is approximately $150,000-300,000 in additional wealth at retirement — the difference between tax-smart and tax-naive investment management over 30 years. Most of this benefit comes from three decisions made once: choosing the right account types, maximizing employer match, and selecting low-cost index funds.
For retirement and tax calculations specifically, consider running this calculation once per year as your income, tax brackets, and contribution limits change. The IRS adjusts dozens of thresholds annually for inflation — limits that applied in 2023 differ meaningfully from 2026 figures. Bookmark this page and revisit each January after the new limits are announced.
Finally, remember that financial optimization is a long game. Improving your savings rate by 5%, reducing investment fees by 0.5%, and claiming every eligible deduction compound over decades into very large differences in final wealth. Small improvements made consistently outperform dramatic one-time decisions every time.