Down Payment Analysis
Every down payment level from 3% to 30%, side by side on your numbers. See how much cash you need at closing, what mortgage insurance costs, and how the monthly payment, lifetime interest and total cost move as you put more down.
There is no single “best” down payment. A larger down payment lowers the monthly payment and can avoid mortgage insurance, but ties up cash you might need elsewhere. This tool shows the trade-off in numbers; the choice is yours.
| Down | Cash required | Loan amount | Mortgage ins. / mo | Monthly payment | Lifetime interest | Total cost |
|---|---|---|---|---|---|---|
| 3% down | $30,000 | $485,000 | $606 | $4,347 | $642,814 | $737,839 |
| 5% down | $40,000 | $475,000 | $396 | $4,072 | $629,560 | $692,060 |
| 10% down | $65,000 | $450,000 | $281 | $3,796 | $596,425 | $638,425 |
| 15% down | $90,000 | $425,000 | $177 | $3,531 | $563,290 | $586,790 |
| 20% down | $115,000 | $400,000 | — | $3,192 | $530,156 | $545,156 |
| 25% down | $140,000 | $375,000 | — | $3,031 | $497,021 | $512,021 |
| 30% down | $165,000 | $350,000 | — | $2,869 | $463,886 | $478,886 |
Rate assumption: 6.71%. Data source: Freddie Mac PMMS national 30-year average (2026-09-03). Calculated: 2026-09-21.
How each row is built
- • Loan amount = price − down payment.
- • Mortgage insurance = conventional PMI by LTV band; it is 0 at 20% down and drops once the balance reaches 80% LTV.
- • Monthly payment = principal + interest + property tax + insurance + mortgage insurance.
- • Cash required = down payment + an estimated 3% of price for closing costs.
- • Total cost = lifetime interest + lifetime mortgage insurance + closing costs.
Go deeper
- Scenario Engine — compare selected scenarios directly
- PMI calculator — mortgage insurance by credit tier
- Closing costs calculator — cash-to-close detail
- Affordability calculator — what price fits your income
- Down payment assistance programs — help with the cash
Methodology & Assumptions
How this calculator works, what it assumes, and where it falls short. Every calculator on TruePITI documents its math.
Formula
- P&I = L · r(1+r)^n / [(1+r)^n − 1]. For each ladder level: L = price − down; mortgage insurance = L · PMI-tier; total cost = lifetime interest + lifetime mortgage insurance + estimated closing costs.
Assumptions
- Fixed-rate fully-amortized loan. Default rate 6.71% is the Freddie Mac PMMS national 30-year average (2026-09-03).
- Mortgage insurance uses conventional PMI tiers (good-credit band); FHA/VA/USDA have different rules.
- Closing costs are estimated at 3% of price, not a lender quote.
Limitations
- Does not model lender down-payment-specific pricing (some lenders price differently by LTV).
- Excludes down-payment assistance and gift funds, which change the cash picture.
- Assumes the mortgage insurance tier for one credit band.
Sources
- Freddie Mac Primary Mortgage Market Survey (PMMS)
- CFPB — down payments and mortgage insurance
Last updated: 2026-09-21. Estimates only — verify rates and costs with your lender.