Note that for every dollar you put into a U.S. bank account that's subject to reserve requirements (I believe just checking accounts?), the bank can loan out much more than 1 dollar, based on the legally required liquidity ratio or "reserve requirement ratio."
Note also that since 2020 that reserve requirement ratio is zero.
A zero percent reserve requirement does not lead in all cases to infinite inflation, because banks are also afraid of a default. Bank's desire to avoid defaults adds another fraction to their reserve ratio and limits money multiplication even when the Fed would technically allow it to proceed infinitely.
Another thing you should know is that Fed chairmen have said that Friedman's equation underestimates bank's ability to create money, because in practice the Fed will allow any bank that desires liquidity to borrow it. The Fed, especially post-great-depression, will happily loan banks however much they needed to cover their reserve requirements, meaning that even before the ratio was set at zero, the number of times a single dollar could be spent was decided primarily by a balance of interest rates and fear of defaults.
at the end of every month and especially every quarter the bank submits its capital ratio and a bunch of other calculations to the regulators. if the ratio isn't good it has to increase capital reserves. if the ratio is good it can do share buybacks and dividends.
They can't loan out more than the deposits they have.
If you could open a bank, accept 10 dollars in deposits, and loan out 100, you'd do it! You'd loan it out to your best friend and keep the cycle going until you're rich AF.
You can't loan out more than you have, but even loaning out 10 of 10 dollars has some risk - if someone comes for their money and you can't get your money back from the people you loaned it to. And it definitely increases money in circulation since it's not parked there. But it's not a magic money printing machine.
Bank regulations have moved one from having such a specific requirement. Nowadays, you essentially need a minimum amount of equity per risk-weighted assets. So you need something like $8 in cash for every $100 in loans you give out.