A US mortgage lender prices a conventional loan off where your credit score sits against cut-off points called tiers. Cross into a higher tier and the rate on offer can drop by a quarter of a percentage point or more.
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That gap is not small. On a US conventional mortgage, a rise from a 670 score to 700 can improve the rate by 0.25 percentage points or more, according to Jeremy Schachter, branch manager at lender Fairway Independent Mortgage Corporation. On a home bought at the recent US average price of $534,000, that difference can cut a monthly payment by nearly $100. Over a 30-year loan it can cut the total interest paid by more than $30,000.
What the file actually holds
Three credit reference agencies collect the data lenders use: Experian, Equifax, and TransUnion. Each holds your history of paying bills, loans, and cards on time, how many times you have applied for credit recently, how much you currently owe, and whether you are on the electoral roll.
In the UK, none of that is the “score” you see in an app. The score is each agency’s own summary of the file, built to its own model, and it is not the number a lender actually consults. Lenders build their own scoring systems from the same underlying file, and how they weigh each factor is not published.
For a US conventional mortgage, lenders take the middle of a borrower’s three bureau scores rather than any single one. If a borrower’s three scores are 680, 700, and 715, the lender prices the loan off 700, says Kevin Havard, founder of MortgageLoans.net. Where two people apply together, the lender uses the lower of their two middle scores.
Where the tiers sit
Havard says conventional US mortgage lenders price loans in roughly 20-point tiers, from 580 up to 760 and beyond. Three points on that scale matter most:
- 620 to 639 is the usual minimum for a conventional loan.
- 680 to 699 brings a noticeable improvement in the rate on offer compared with scores below it.
- 760 and above reaches the best rates lenders offer.
Moving up a tier can have a significant effect on the rate for some borrowers. A government-backed US loan works differently. Loans through the Federal Housing Administration, the Department of Veterans Affairs, and the Department of Agriculture generally need a score of at least 580. Schachter says their rates barely move once a borrower clears 640: someone with a 760 score gets much the same rate as someone with 640. For FHA loans, the score changes the down payment instead: 3.5% at 580 or above, and at least 10% for a score between 500 and 579.
Why UK lenders work from the same file, differently
British lenders never see a single market-wide score at all. Each of the UK’s three agencies scores you on its own range: 0 to 999 at TransUnion after a September 2026 change from its old top mark of 710, 0 to 1,000 at Equifax, and 0 to 1,250 at Experian. A UK lender ignores those numbers and goes straight to the same file: your payment history, how much you owe, and how you have used credit over time.
That is why TransUnion’s rescoring, which will move 36% of customers into a higher band and 6% into a lower one by the time it finishes rolling out in June 2027, does not itself change anyone’s mortgage or loan prospects. Tom Eyre, chief executive of the credit-building platform Loqbox, says a lower band after a rescoring does not mean someone has “become less creditworthy overnight.” Their history has not changed, only how the agency presents it.
What actually moves the needle
Whichever side of the Atlantic you borrow on, the factors behind the rate are the same kind of thing: a history of paying on time, how much you owe, and how many recent applications sit on your file. In the UK, the number displayed in a banking app is one agency’s view of that file, not the input a lender decides on.
Eyre’s advice follows from that: understanding what shapes the report matters more than watching a single band or number, because those underlying details are what a lender actually weighs.
