Borrowers paying interest on a car loan or mortgage see a figure called the annual percentage rate, or APR, on their disclosures. Savers parking cash in a deposit account see a different metric, the annual percentage yield, or APY. These two numbers are calculated under separate federal rules, and the spread between what banks charge on loans and what they pay on deposits feeds directly into industry profits. With FDIC-insured institutions reporting net interest margin data through the second quarter of 2025, and JPMorgan Chase filing its annual report for the year ended December 31, 2025, the mechanics behind that spread deserve close attention from anyone on either side of a bank counter.
How the APR–APY spread drives bank earnings right now
Banks earn money on the difference between the interest they collect from borrowers and the interest they pay to depositors. That difference, known as net interest margin, or NIM, is the single largest revenue driver for many commercial banks. The industry-wide figures in the FDIC banking profile tie aggregate profitability to the gap between yields on loans and securities and the cost of deposits and other funding. When loan APRs stay elevated while savings APYs adjust more slowly, that margin widens and bank earnings tend to rise.
At the firm level, JPMorgan Chase’s net interest story is spelled out in its 2025 annual report. The filing shows net interest income as the difference between interest earned on assets such as mortgages, credit cards, and commercial loans, and interest paid on deposits and wholesale funding. Even without product-by-product APR and APY data, the report makes clear that higher asset yields relative to funding costs flow directly into reported profit. This is not an abstract accounting concept; it is the core business model of deposit-taking institutions.
The intuitive hypothesis is that banks with the widest quarterly net interest margins also display the largest gaps between advertised loan APRs and savings APYs. A lender charging double-digit APRs on credit cards while paying only a fraction of a percent on checking and savings would, in theory, post a robust margin. Yet confirming that intuition is difficult using public data alone. Regulatory filings aggregate interest income and interest expense across many products, maturities, and customer segments. They do not pair a specific credit card APR with a contemporaneous savings APY for the same bank, which means the relationship between posted retail rates and overall NIM cannot be tested with precision from current disclosures.
Regulation Z and Regulation DD define each side of the gap
The existence of two different yardsticks-APR for loans and APY for deposits-traces back to separate disclosure regimes created by Congress and implemented by federal regulators. On the lending side, the Truth in Lending Act and its implementing rule, Regulation Z (12 CFR Part 1026), require creditors to quote the APR on most consumer loans. Under this framework, the APR is designed to capture not only the nominal interest rate but also certain finance charges paid by the borrower, expressed as a yearly rate. The Consumer Financial Protection Bureau’s own explainer distinguishes the APR from the simple interest rate, emphasizing that the broader measure helps consumers compare the true cost of credit across lenders and products.
For deposit accounts, Congress took a different approach. The Truth in Savings Act led to Regulation DD, which standardizes how banks must disclose the return on consumer deposit products. The CFPB’s version of Regulation DD defines APY as a measure that reflects the effect of compounding over a one-year period, assuming funds remain on deposit and interest is not withdrawn. Where APR is meant to aggregate the cost of borrowing, APY is meant to aggregate the benefit of saving, allowing consumers to compare offers even when banks compound interest on different schedules or quote slightly different nominal rates.
These technical differences matter. A loan and a deposit could share the same nominal interest rate, yet the borrower’s APR might be higher once fees are included, while the saver’s APY might be higher or lower depending on how often interest compounds. From the bank’s perspective, however, the key economic variable is simpler: the average yield on its interest-earning assets versus the average cost of its interest-bearing liabilities. The regulatory definitions help shape consumer understanding but do not change that underlying arithmetic.
Why the spread is hard for consumers to see
Consumers encounter APR and APY in separate contexts-loan paperwork on one side, account-opening disclosures on the other. Regulations require clear presentation within each silo, but there is no mandate for banks to show a side-by-side comparison of what they charge borrowers versus what they pay savers. As a result, the net interest margin that dominates bank earnings reports is largely invisible at the branch or app level.
Public data sets only partially fill that gap. The FDIC’s aggregate statistics reveal how margins move over time as interest rates change, and large banks’ annual reports explain, in broad strokes, how shifts in asset yields and deposit costs affect net interest income. Yet neither source breaks down the precise relationship between specific APRs and APYs at a given institution and moment in time. For now, anyone trying to understand how their personal loan rate and savings yield feed into a bank’s profits must infer the connection from these high-level disclosures rather than from a single, unified snapshot.
Warren Cohen is a finance writer based in Phoenix, Arizona, covering personal finance topics including credit, banking, and beginner investing. He earned his degree in business administration from Arizona State University and began his career working in consumer finance, where he gained direct experience with lending and credit systems. He now writes for personal finance websites and fintech platforms, focusing on clear, practical content that helps readers make informed financial decisions.
