Loan-to-Value Ratio, Explained: Why 80% Is the Line That Matters
By the Stoia team · September 7, 2026 · 5 min read
Borrow $360,000 against a $400,000 house and your loan-to-value ratio is 90%. That one number is why the buyer pays mortgage insurance, why the rate quote came in a notch above a neighbor's, and why a cash-out refinance is off the table for a few years. Outside of the credit score, no single input decides more about a mortgage than LTV, and unlike the credit score it is simple enough to work out on a napkin.
The formula
The loan-to-value ratio is the loan balance divided by the property's value. At purchase, lenders use the lower of the price and the appraised value; afterward, it is the current balance against whatever the home is worth now. Twenty percent down is an 80% LTV, 5% down is 95%, and the $360,000 loan on the $400,000 house is $360,000 / $400,000 = 90%. LTV is simply the mirror image of your equity share: 90% LTV means you own 10% of the house and the lender is exposed on the rest, which is exactly how the lender reads it.
Why 80% is the magic line
Lenders treat 80% as the point where their risk becomes acceptable without extra protection, and two costs turn on it.
- Mortgage insurance. Conventional loans above 80% LTV require private mortgage insurance, which protects the lender, not you. Premiums are set by the market and commonly quoted from a few tenths of a percent up to around 1.5% of the loan per year; at 0.6%, the $360,000 loan carries about $180 a month. Federal law gives you the right to request cancellation once the balance reaches 80% of the original value, assuming payments are current, and requires the insurer to drop off automatically at 78% on the original schedule. Many servicers also honor a request based on a fresh appraisal, subject to their own seasoning rules. The mechanics are covered in PMI, explained.
- Refinance pricing. Refinance rates are priced in LTV bands, and each step down (below 80%, below 70%, below 60%) tends to shave the adjustments a lender adds to the base rate. A refinance below 80% also escapes mortgage insurance entirely, and cash-out refinances are usually capped at 80% LTV, which is why a recent buyer cannot pull cash out even if the house has risen a little. The refinance calculator shows whether the rate you would qualify for at your LTV is worth the closing costs.
Combined LTV
Once a second loan sits on the house, the ratio that matters is combined LTV: every lien added together, divided by the value. Five years into the example, the first mortgage is down to about $337,000 and the house, growing 3% a year, is worth about $463,700. Add a $35,000 home equity line and the combined LTV is $372,000 / $463,700, or about 80%. Home equity lenders generally stop lending somewhere around 80–85% combined, which is why the amount you can borrow against a house is not your equity, it is your equity above the lender's line.
How LTV falls over time
Two forces push the ratio down: the balance shrinks through amortization, and the value tends to rise. The table follows the example loan for ten years and shows both versions of the ratio, because they answer different questions. The original-value column is what the automatic PMI schedule uses; the current-value column is what a new appraisal would show.
| Year | Balance | LTV vs. original $400,000 | Value at 3%/yr | LTV vs. current value |
|---|---|---|---|---|
| 0 | $360,000 | 90.0% | $400,000 | 90.0% |
| 1 | $356,000 | 89.0% | $412,000 | 86.4% |
| 2 | $351,700 | 87.9% | $424,400 | 82.9% |
| 3 | $347,100 | 86.8% | $437,100 | 79.4% |
| 4 | $342,200 | 85.6% | $450,200 | 76.0% |
| 5 | $337,000 | 84.2% | $463,700 | 72.7% |
| 6 | $331,400 | 82.9% | $477,600 | 69.4% |
| 7 | $325,500 | 81.4% | $492,000 | 66.2% |
| 8 | $319,200 | 79.8% | $506,700 | 63.0% |
| 9 | $312,400 | 78.1% | $521,900 | 59.9% |
| 10 | $305,200 | 76.3% | $537,600 | 56.8% |
On the original value, the 80% line arrives during year eight and the automatic 78% cutoff around year nine. On current value, with modest 3% growth, the ratio crosses 80% in year three. That gap is roughly five years of a $180 premium, close to $10,000, which is the strongest argument for paying for an appraisal and asking once you believe the house has appreciated. The PMI calculator estimates both the monthly cost and the removal date on your own loan. The LTV calculator gives you the ratio itself, combined LTV included, in seconds.
A worked example: buying the line down faster
Suppose the buyer wants to hit 80% of the original value without waiting on the market. The balance needs to fall from $360,000 to $320,000, and the regular payment of about $2,275 gets there in just under eight years. Add $200 a month of extra principal and it arrives in about five years and four months instead, roughly two and a half years sooner. At $180 a month that is about $5,600 of insurance premiums never paid, on top of the interest saved by carrying a smaller balance. Extra principal is one of the few moves that improves both columns of the table at once, because every dollar lowers the balance regardless of what the appraisal says.
When LTV works against you
Above 100%, the loan exceeds the value and the house is underwater: no refinance will clear, and a sale means bringing cash to closing. That is the real risk of the minimal-down programs that allow LTVs well into the 90s. They are the right tool for buyers who would otherwise rent for years, but they leave almost no cushion, and a 10% price drop erases it entirely. A high LTV is not a mistake; it is a position with less room for error, and the response is to treat the early years as the time to build the cushion rather than to borrow against it.
LTV is a ratio between two numbers that both move every month, and the cleanest way to watch it is to keep the balance and the home value side by side. Stoia tracks both, so the line you are working toward is visible long before the lender mentions it.