Twenty percent down is the number everyone repeats. Parents say it, agents say it, the guy at the hardware store says it. Usually it gets framed as a way to skip private mortgage insurance, which is true, but it undersells what’s actually happening. The size of your down payment is one of the few levers that moves the interest rate itself, not just the monthly bill attached to it.
Here’s what that pricing really looks like, and where the savings turn out bigger or smaller than most buyers expect.
Two separate things happen at 80% loan-to-value
Lenders don’t price mortgages on your down payment percentage. They price on loan-to-value, or LTV, which is simply the loan amount divided by the home’s appraised value. Put 20% down on a $400,000 house and your LTV is 80%. That one number triggers two changes at the same time.
The first is mortgage insurance. On a conventional loan above 80% LTV, you’re typically paying 0.3% to 1.1% of the loan balance each year for coverage, depending on credit. On a $360,000 loan that runs somewhere between $90 and $330 a month, and not one dollar of it touches your principal.
The second change is quieter and gets far less airtime. Most lenders build rate sheets in 5% LTV bands, and each band you drop gets slightly cheaper. The gap between 85% and 80% is usually the widest single step on the whole grid, which is the real reason 20% down earned its reputation.
The loan-to-value bands that decide your rate
A typical conventional rate sheet stacks up roughly like this before any credit adjustments get applied:
- 95% LTV (5% down): highest pricing, mortgage insurance required
- 90% LTV (10% down): usually 0.125% to 0.25% better than 95%
- 85% LTV (15% down): a smaller step down, PMI still applies
- 80% LTV (20% down): PMI falls away and the rate falls with it
- 75% LTV (25% down): a modest additional discount at many lenders
- 60% LTV (40% down): the best conventional pricing tier, though the gain is small
Look at the shape of that curve. The big jump sits between 85% and 80%. Past that point, each extra 5% of equity buys you less and less. Moving from 20% down to 25% down might shave 0.125% off the rate, which on a $300,000 loan works out to about $22 a month. Worth having, not worth gutting your savings account for.
Running the numbers on a $400,000 purchase
Put two buyers side by side. Both have a 740 middle credit score, both are buying the same $400,000 house on the same afternoon.
Buyer one puts 10% down. That’s a $360,000 loan priced around 6.875%, plus mortgage insurance at roughly 0.5% of the balance annually. Principal and interest come to about $2,365, PMI adds roughly $150, so the housing payment lands near $2,515 before taxes and homeowners insurance.
Buyer two puts 20% down. That’s a $320,000 loan priced closer to 6.50%, no mortgage insurance. Monthly principal and interest: about $2,023.
Part of that $490 gap is simply borrowing $40,000 less. Isolate the rate and it’s still meaningful. On an identical $360,000 balance, 6.50% versus 6.875% costs about $90 a month, which compounds into roughly $32,000 of extra interest over 30 years. That’s the piece people miss when they treat 20% down as purely a PMI question.
Your credit score still sets the starting line
Down payment and credit score are two separate dials, and the credit dial has more range. Someone with a 780 score putting 10% down will often beat a 660 borrower putting 25% down on rate, even after the loan-level price adjustments that hit high-LTV loans.
If your mid-score is 760 or above, 20% down stacks on top of pricing that’s already near the floor. What a 760+ score really buys you is a useful baseline, because it shows how little room is left for a bigger down payment to improve things once credit is excellent.
Below 680 the picture flips. LTV adjustments get larger, so the 80% threshold matters more rather than less. A borrower at 620 putting 5% down is paying for both problems at once, and that combination is where quotes start to look genuinely ugly. If your score sits in that range, it’s worth knowing what borrowers actually pay at 580, 600 and 620 before you assume a bigger down payment will fix the rate on its own.
When 20% down doesn’t rescue you
There are situations where handing over a fifth of the purchase price does far less than expected.
Thin credit files are the clearest case. A buyer with three years of history and no installment loans can put 30% down and still land in a mid-tier pricing bucket, because the lender is pricing uncertainty about repayment, not uncertainty about equity. Self-employed borrowers with heavy write-offs run into the same wall.
Cash reserves are the other trap. Lenders want to see two to six months of payments left over after closing, and some price the loan worse when reserves are thin. Draining every account to reach 20% down can quietly cost you a quarter point, which cancels out most of what you gained. On a $320,000 loan, keeping $15,000 in reserve instead of putting it into the house is often the better trade even though the rate ticks up slightly.
Points, down payment, or cash in the bank
Discount points are the comparison most buyers never run. One point costs 1% of the loan amount and typically buys 0.25% off the rate. On a $320,000 loan, that’s $3,200 upfront for a payment reduction of about $52 a month. Break-even arrives around month 61, so if you plan to stay past five years, buying the rate down can outperform putting that same $3,200 toward a larger down payment.
What you shouldn’t do is stretch for 20% down and then take a worse rate because your reserves got thin or you financed closing costs. If 15% down with a comfortable cushion gets you a 6.625% rate and 20% down with nothing left over gets you 6.75%, the smaller down payment wins on total cost.
Timing deserves a mention too. If your purchase is a year or two out, the rate you’re quoted today is not the rate you’ll sign for. Sketching out the realistic range for mortgage rates in 2027 helps you decide how much house to commit to now versus how much to hold back.
Loan size changes the whole calculation
A $250,000 loan and a $750,000 loan don’t price the same way even with identical LTV and credit. Crossing the conforming loan limit pushes you into jumbo territory, where lenders care more about reserves, and where a 20% down payment is often a hard requirement rather than a discount. In high-cost metros, 20% down on a $900,000 purchase means $180,000 in cash, which is a completely different conversation than the same percentage on a $300,000 starter home.
There’s also a subtler effect: larger loans sometimes price better in rate terms but worse in dollar terms because every eighth of a point is worth more. Why $250K and $750K don’t price the same digs into the agency pricing grids behind that, and it’s worth reading before you assume your quote scales proportionally.
What to ask before you commit the cash
By the time you have a Loan Estimate in hand, the down payment decision is mostly locked in. Ask these questions earlier, ideally while you’re still comparing two or three lenders.
- What is my exact LTV, and does dropping to the next band down change my rate? Ask for the rate at both levels in writing.
- How much of my quoted rate is a lender credit, and what happens to it if my appraisal comes in low and my LTV rises above 80%?
- What reserves do you require after closing, and does my pricing change if I keep more cash back?
- What is the rate with and without points, side by side, with the break-even month calculated?
- Is this loan eligible for PMI removal at 80% of the original value, and do you require a new appraisal to do it?
That last one matters more than it sounds. Lenders must terminate mortgage insurance at 78% LTV on the original amortization schedule, but you can usually request removal at 80% based on the original value, which may happen years sooner. A borrower who bought with 10% down and watched the market climb can often drop PMI without refinancing at all, and the request is on them to make.
Run the 20% down scenario against 15% and 25% with your actual numbers, not a rule of thumb. The right answer depends on your credit tier, your reserves, how long you plan to stay, and whether the money would otherwise sit in a savings account earning 4%. Sometimes the fifth of the purchase price is the best deal on the table. Sometimes it’s a rounding error next to what a 40-point credit improvement would do.