🏦 Fractional Reserve Fractional Reserve
A banking system where the bank keeps only a small slice of customer deposits on hand and lends out the rest. It puts idle money to work, but it also means the bank can't hand back every deposit at the exact same moment.
🏦 The simple version — money that keeps working
When you deposit money, a bank doesn't lock it in a drawer with your name on it. It keeps a small fraction on hand and lends the rest to other people as loans. Those loans become someone else's deposit, get re-lent, and the cycle repeats. This is fractional reserve banking, and almost every bank in the world runs on it.
🔁 The money multiplier — how $1,000 becomes much more
Say a bank keeps 10% and lends 90%. Your $1,000 turns into $100 kept + $900 lent. That $900 gets spent, lands in another bank, which keeps $90 and lends $810. Repeat that down the chain and the total money supply expands far beyond your original deposit — without anyone printing a single new bill.
| Round | Deposited | Kept (10%) | Lent on |
|---|---|---|---|
| 1️⃣ You | $1,000 | $100 | $900 |
| 2️⃣ Next bank | $900 | $90 | $810 |
| 3️⃣ Next bank | $810 | $81 | $729 |
📊 The money supply grows because the same dollars get counted in many accounts at once. It's a feature that fuels loans and the economy, not a glitch.
📜 The reserve requirement — and why it's now zero in the US
A reserve requirement is the legal minimum fraction a bank must hold. On March 26, 2020, the US Federal Reserve cut this requirement to zero percent, freeing roughly $200 billion. That does not mean banks hold nothing — they still keep reserves voluntarily for liquidity under what the Fed calls an "ample reserves" regime. The legal floor is gone, but the reserves aren't.
🚨 The catch — a bank run
The whole system rests on one bet: not everyone asks for their money at the same time. If too many depositors rush to withdraw at once — a bank run — the cash simply isn't there, because it's been lent out. The model works in calm times and breaks under panic.
🪙 Why this matters in crypto
Bitcoin and most cryptocurrencies are built on the opposite idea: no central authority lending your coins out, and a supply that's capped or fixed by code (Bitcoin caps at 21 million). Where the debate gets real is stablecoins. Most big fiat-backed ones — like USDC and USDT — claim to be fully reserved (one token, one unit of safe assets, redeemable on demand). A fractional-reserve stablecoin would back tokens with only part of that — more scalable, but it can face a run just like a bank, often with no deposit insurance and no central-bank backstop.
🔍 This is where a beginner meets the term: "is my stablecoin or exchange actually holding 1:1, or running fractional reserve?" That question is exactly what proof-of-reserves audits try to answer.
❓ FAQ
- If the bank lent out my deposit, is my money gone?
- No, your balance is still yours to spend or withdraw on a normal day. The bank only keeps a fraction of all deposits as cash because it assumes everyone won't ask for their money at the same moment. The risk shows up only if too many people withdraw at once — that's a bank run.
- Does a zero reserve requirement mean banks hold no reserves?
- No. In March 2020 the US Federal Reserve cut the legal minimum reserve ratio to zero percent, but banks still keep reserves voluntarily for liquidity and safety. The legal floor is gone, not the reserves themselves.
- Are stablecoins fractional reserve too?
- It depends on the token. Most major fiat-backed stablecoins claim to be fully reserved — one token backed by one unit of safe assets, redeemable on demand. A fractional-reserve stablecoin would hold reserves worth only part of the tokens issued, which is more scalable but riskier, often with no deposit insurance or central-bank backstop.