Short answer: The median FDIC-insured bank ran a net interest margin of 3.83% in the quarter ending June 30, 2026. Half of all banks fell between 3.34% and 4.32%. Anything above roughly 4.3% is top-quartile; below 3.3% is bottom-quartile. But NIM is only meaningful against banks of similar size, and the spread by size is wide: the median bank over $100B earned 3.09%, while the median bank between $100M and $300M earned 3.93%.
The 2026 benchmark, by bank size
Net interest margin is the spread a bank keeps between what it earns on loans and securities and what it pays for deposits and borrowings. It is the single most-quoted measure of a bank's core earnings engine, and the most commonly misread, because a number that looks strong for a $50 billion bank would be mediocre for a $200 million one.
Here is the full distribution for every filing bank in the quarter ending June 30, 2026.
| Bank size (total assets) | Banks | Bottom quartile | Median | Top quartile |
|---|---|---|---|---|
| All banks | 4,282 | 3.34% | 3.83% | 4.32% |
| Under $100M | 572 | 3.34% | 3.85% | 4.48% |
| $100M - $300M | 1,222 | 3.42% | 3.93% | 4.42% |
| $300M - $1B | 1,435 | 3.41% | 3.88% | 4.30% |
| $1B - $3B | 629 | 3.26% | 3.69% | 4.12% |
| $3B - $10B | 265 | 3.21% | 3.64% | 4.06% |
| $10B - $100B | 127 | 3.18% | 3.57% | 3.92% |
| Over $100B | 32 | 2.11% | 3.09% | 3.68% |
Source: BankingLens, computed from FFIEC call reports for the quarter ending June 30, 2026. Quartiles are calculated across the full population of filing banks in each size band, not sampled.
The pattern in that table
Margin peaks in the $100M to $1B range and falls steadily above it. That is not a sign that small banks are better run. It reflects three structural differences that have nothing to do with management quality.
Small banks fund themselves more cheaply. Their deposits are local, sticky, and disproportionately non-interest-bearing checking accounts. The median bank under $100M paid a 2.01% cost of funds in Q2 2026; the median bank over $100 billion paid 2.63%. That 62 basis point gap flows almost directly into margin.
Large banks lend at thinner spreads. They compete for national, investment-grade, and syndicated credits where pricing is set by a market rather than a relationship. A community bank pricing a local operating line has far more discretion.
Large banks also earn far more non-interest income. Card, wealth, treasury management, and capital markets revenue never touch net interest margin, so the ratio understates their earnings power. The median bank over $100 billion earned a 1.20% return on assets, essentially identical to the 1.23% industry median, on a margin roughly 74 basis points thinner.
What actually moves a bank's NIM
Deposit mix is the largest lever and the slowest to change. Non-interest-bearing checking balances cost nothing, so a bank whose funding is 30% non-interest-bearing starts every quarter ahead of one at 10%. That mix is built over years through operating relationships, which is why banks fight so hard for a business's primary checking account.
Asset mix is the second lever. Loans yield more than securities, so a bank with a 90% loan-to-deposit ratio will generally out-earn one at 50% on margin alone. The tradeoff is liquidity and credit risk, and the bank at 50% has room to grow that the bank at 90% does not.
Rate positioning is the third. A bank with mostly floating-rate commercial loans repriced quickly as rates rose; one holding long fixed-rate mortgages and municipal bonds did not, and is still earning yields set years ago. This is why two banks in the same town with the same deposit base can post margins 100 basis points apart.
How to use this number
If you are benchmarking your own bank, compare against your asset band in the table above, not the all-bank median. Then look at whether your margin is being driven by cheap funding or by high asset yields, because those two paths carry very different risk. A bank earning a 4.2% margin on cheap core deposits is in a much stronger position than one earning 4.2% by reaching for yield in its loan book.
If you are a business trying to borrow, margin tells you something useful but not what most people assume. A bank with a compressed margin is under pressure to book higher-yielding loans, which makes it motivated to win your business. It does not mean the bank can quote you a cheaper rate. The ability to cut price comes from cheap funding, not from a thin margin, and those are close to opposite conditions.
Frequently asked questions
What is a good net interest margin for a bank?
The median US bank ran a 3.83% net interest margin in the quarter ending June 30, 2026, with the middle half of banks between 3.34% and 4.32%. A NIM above about 4.1% puts a bank in the top quartile nationally. Because margin varies systematically with bank size, the more useful comparison is against banks in the same asset band.
What is the average net interest margin for community banks in 2026?
Community banks under $1 billion in assets ran higher margins than the industry overall. The median was 3.85% for banks under $100M, 3.93% for banks between $100M and $300M, and 3.88% for banks between $300M and $1B, versus 3.09% for banks over $100 billion.
Why do large banks have lower net interest margins?
Large banks fund themselves with more wholesale and interest-bearing money, hold larger securities portfolios at lower yields, and compete for the most creditworthy borrowers at the thinnest spreads. They also earn much more fee income, so a lower margin does not mean lower profitability. The median bank over $100 billion earned a 3.09% NIM but a 1.20% return on assets, roughly the industry median.
Is a higher net interest margin always better?
No. A very high NIM can reflect higher-risk lending, concentration in a single high-yield product, or a subprime consumer book, and it usually comes with higher credit costs later. Margin should be read alongside the non-performing loan ratio and the efficiency ratio, not on its own.
How is net interest margin calculated?
Net interest margin is net interest income, meaning interest earned on loans and securities minus interest paid on deposits and borrowings, divided by average earning assets. It is reported quarterly by every FDIC-insured bank in its FFIEC call report.
Where these numbers come from
Every figure on this page is computed from the FFIEC call reports that all 4,296 FDIC-insured banks file each quarter, for the quarter ending June 30, 2026. Nothing here is modeled, estimated, or sampled. You can pull any individual bank behind these distributions on Bank Peer Intel, or, if you are trying to borrow rather than benchmark, see which lenders these numbers point to on Borrower Assist.