Reserve Ratio Calculator — Money Multiplier & Required Reserves
Understand fractional-reserve banking: enter total deposits and the required reserve ratio to see how much a bank must hold in reserve, how much it can lend, and how many times the original deposit can be multiplied through the banking system.
%
Maximum money supply created per unit of base money deposited
- 1
Required reserves
1,000,000 × 10% ÷ 100 = 100,000 - 2
Loanable funds
1,000,000 − 100,000 = 900,000 - 3
Money multiplier
100 ÷ 10 = 10Each unit of base money can theoretically support this many units of total money supply.
How does this calculator work?
Required reserves = deposits × reserve ratio. Money multiplier = 1 ÷ reserve ratio. Maximum total money supply = deposits × multiplier. At a 10% reserve ratio, a $1,000,000 deposit base requires $100,000 in reserves, leaves $900,000 loanable, and can theoretically support a $10,000,000 money supply through the lending chain.
Formula
How this is calculated
In a fractional-reserve banking system, banks are required to hold only a fraction of their deposits in reserve (as cash in vault or deposits at the central bank). The rest — the loanable funds — can be lent out. Those loans become deposits elsewhere in the banking system, which are again partially lent out, and so on. This cascading process is the money multiplier effect.
The required reserve ratio (RRR) is set by the central bank and represents the minimum fraction of deposits that must be kept in reserve. Required reserves equal deposits multiplied by the RRR. Loanable funds are the remainder. The theoretical money multiplier is 1 ÷ RRR: a 10% reserve ratio implies a multiplier of 10, meaning $1 of base money deposited can ultimately support $10 in the total money supply through repeated lending.
In practice, the actual multiplier is lower than the theoretical maximum because banks hold excess reserves (beyond the minimum), some currency leaks out of the banking system as physical cash, and not all loans are immediately re-deposited. Since 2020, the US Federal Reserve has set the required reserve ratio at 0%, relying on other tools to manage the money supply. Enter the actual reserves held (if known) to compute excess reserves and the real reserve ratio. These are estimates based on simplified assumptions; actual monetary policy effects are more complex.
Frequently asked questions
Many central banks have shifted away from reserve ratio requirements as a primary monetary policy tool. The US Federal Reserve reduced the requirement to 0% in March 2020. The ECB and Bank of England use a 1% minimum ratio. Canada, Australia, New Zealand and Sweden have no formal reserve requirement. Check your central bank's current policy for the exact figure.
Excess reserves are the amount a bank holds above the required minimum. Banks may hold excess reserves to manage liquidity risk, because the central bank pays interest on reserves (in the US, IOER/IORB), or during periods of uncertainty when lending opportunities are limited. Excess reserves reduce the effective money multiplier.
Yes — a higher reserve ratio reduces the money multiplier and limits how much banks can lend, contracting the potential money supply. A lower ratio allows more lending and expands it. Central banks historically raised reserve requirements to cool inflation and cut them to stimulate lending, though modern central banks now primarily use interest rates and open-market operations for this purpose.
Also known as
TG we-Calculate Editorial Team. (2026). Reserve Ratio Calculator — Money Multiplier & Required Reserves [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/reserve-ratio-calculator
TG we-Calculate Editorial Team. "Reserve Ratio Calculator — Money Multiplier & Required Reserves." TG we-Calculate. 2026. https://we-calculate.com/calculator/reserve-ratio-calculator.
TG we-Calculate Editorial Team, "Reserve Ratio Calculator — Money Multiplier & Required Reserves," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/reserve-ratio-calculator
@misc{wecalculate_reserve_ratio_calculator, title = {Reserve Ratio Calculator — Money Multiplier & Required Reserves}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/reserve-ratio-calculator}}, year = {2026}, note = {TG we-Calculate} }
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