How Your Down Payment Affects Your Mortgage
A bigger down payment does four things at once — it cuts your loan, lowers your rate risk, can erase mortgage insurance, and shrinks the interest you pay for decades.
More than just "money down"
A down payment feels like a hurdle — the cash you have to scrape together before anyone hands you keys. But it's doing far more than getting you in the door. The size of your down payment quietly sets your loan-to-value ratio, decides whether you pay mortgage insurance, and shapes both your monthly payment and the total interest you'll pay over decades. It's one of the few levers you fully control, so it's worth understanding what each extra unit of cash actually buys.
Loan-to-value: the number lenders watch
The key metric is loan-to-value (LTV) — the size of your loan as a percentage of the home's price:
LTV = loan amount ÷ home price
On a 300,000 home with 30,000 down, you borrow 270,000, so LTV = 270,000 ÷ 300,000 = 90%. Put 60,000 down and LTV drops to 80%.
Lower LTV means less risk for the lender, and that ripples into everything: better odds of approval, often a better rate, and — crucially — whether you're charged mortgage insurance. The magic threshold almost everywhere is 80% LTV, which is the same as a 20% down payment.
The PMI threshold
If your down payment is under 20% (LTV above 80%), most lenders require private mortgage insurance (PMI) — an extra monthly charge that protects the lender, not you, if you default. It typically runs 0.3%–1.5% of the loan per year.
On a 270,000 loan at, say, 0.7% a year, that's about 1,890 a year — roughly 158 a month — paid on top of your mortgage, buying you nothing personally. Cross the 20%-down line and PMI usually disappears entirely. That single threshold is why "get to 20%" is such common advice: the jump from 19% to 20% down can be worth far more than the cash difference, because it deletes a recurring charge.
A worked example
Same 300,000 home, 30-year loan at 6%. Compare three down payments:
| Down payment | % down | Loan | LTV | PMI/mo | P&I/mo | Total payment/mo |
|---|---|---|---|---|---|---|
| 15,000 | 5% | 285,000 | 95% | ~166 | 1,709 | ~1,875 |
| 30,000 | 10% | 270,000 | 90% | ~158 | 1,619 | ~1,777 |
| 60,000 | 20% | 240,000 | 80% | 0 | 1,439 | 1,439 |
Look at the bottom row. Going from 10% to 20% down cuts the loan by 30,000, which trims principal and interest by about 180 a month — and it also wipes out the 158 of PMI. Together that's roughly 338 a month lower, or about 4,000 a year, for putting in an extra 30,000. A down payment calculator lets you slide the percentage and watch all of this update.
The total-interest effect
The monthly saving is only half the story. A smaller loan means less interest for the entire term. Over 30 years at 6%:
- 285,000 loan → about 330,300 in total interest.
- 240,000 loan → about 278,200 in total interest.
That's roughly 52,000 less interest over the life of the loan from the larger down payment — separate from, and on top of, the PMI you avoided. The reason is straightforward: interest is charged on the balance, so a smaller starting balance accrues less interest every month for 360 months. See how loan amortization works for the month-by-month mechanics, or generate the full schedule on an amortization calculator.
When a smaller down payment makes sense
Bigger isn't automatically better. A few honest counterpoints:
- Don't drain your emergency fund. A home with zero cash reserves is fragile. Keep a buffer even if it means less down.
- Time in the market. If prices or rents are climbing fast, waiting years to reach 20% can cost more than the PMI would have. PMI also ends once you reach 20% equity through payments, so it's temporary.
- Opportunity cost. If your money could earn more elsewhere than the mortgage rate, a smaller down payment can be rational — though that's a bet, not a guarantee.
The point isn't "always put 20% down." It's to make the choice with the full picture: LTV, PMI, payment, and lifetime interest, all at once.
Putting it together
Before you commit, run your real numbers. Set the price and rate on a mortgage calculator, then flex the down payment to see the payment and total interest move in real time. If you're still deciding what you can buy at all, start with how much house can I afford and let the down payment fall out of that budget.
Takeaways
- Your down payment sets LTV — and 80% LTV (20% down) is the line that removes PMI.
- Under 20% down usually means monthly PMI that protects the lender, not you.
- A bigger down payment lowers both the monthly payment and total lifetime interest.
- Don't empty your savings to hit 20% — weigh reserves and opportunity cost too.
Try the calculators
Keep reading
- How Much House Can I Afford?
Your income sets a budget, but your debts, down payment, and interest rate decide the actual price tag — here is how they fit together.
- How Loan Amortization Works (With a Worked Example)
See exactly how each loan payment splits between interest and principal — and when you finally start building real equity.
David writes about borrowing without the jargon, after years of helping friends and family decode loan paperwork. He believes everyone deserves to understand what they’re signing.