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Finance Calc Kit
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Reserve Ratio Calculator

Calculate bank reserve requirements, required vs excess reserves, reserve ratio percentage, and fractional-reserve money multiplier easily.

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Required reserves

$100,000.00

10.0% required ratio (actual: 15.00%)

Excess reserves

$50,000.00

Money multiplier

10.00x

Actual reserve ratio

15.00%

Max money expansion

$500,000.00

Lending capacity

Maximum initial lending capacity equals total deposits minus required reserves.

$900,000.00

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What is a bank reserve ratio?

The reserve ratio is the percentage of customer deposits a bank must hold in vault cash or deposits at the central bank rather than lend out. Regulators set minimum reserve requirements to ensure liquidity and stabilize the fractional-reserve banking system. This calculator computes required reserves, excess reserves, the actual reserve ratio, and the simple money multiplier.

To see how monetary aggregates expand across the broader economy, use the money supply calculator. For macro context on how reserve policy interacts with inflation, see the inflation calculator.

Reserve requirement and money multiplier formulas

Required Reserves=Deposits×Reserve Ratio100\text{Required Reserves} = \text{Deposits} \times \frac{\text{Reserve Ratio}}{100}
Excess Reserves=Reserves Held−Required Reserves\text{Excess Reserves} = \text{Reserves Held} - \text{Required Reserves}
Money Multiplier=1Reserve Ratio as decimal\text{Money Multiplier} = \frac{1}{\text{Reserve Ratio as decimal}}

Maximum potential money supply expansion from excess reserves equals excess reserves multiplied by the money multiplier under the simplified textbook model.

Worked example

A bank with $1,000,000 in deposits, $150,000 in reserves, and a 10% required reserve ratio must hold $100,000 in required reserves. Excess reserves equal $50,000. The actual reserve ratio is 15%. The money multiplier is 10x, so $50,000 in excess reserves could theoretically support up to $500,000 in additional money supply expansion in the simple model.

Key outputs explained

  • Required reserves: Mandatory vault cash or central bank balances.
  • Excess reserves: Reserves above the legal minimum available for lending.
  • Money multiplier: Theoretical deposit expansion per dollar of reserves in the textbook fractional-reserve model.
  • Max lending: Deposits minus required reserves, the initial lending capacity before iterative re-deposit cycles.

Frequently asked questions

Is the money multiplier exact in real economies?
No. The simple multiplier assumes banks lend all excess reserves, borrowers redeposit funds, and no cash leaks from the system. Real-world lending depends on credit demand, capital rules, and central bank policy.
What counts as reserves?
Reserves include physical vault cash plus balances held at the central bank (such as Federal Reserve deposits in the United States).
What if excess reserves are negative?
A negative excess reserve figure means the bank holds less than the regulatory minimum. The institution would need to raise reserves or reduce deposits to comply.
How do reserve requirements vary by country?
Each central bank sets its own rules. Some economies use zero required reserve ratios while still managing liquidity through other tools. Enter the ratio that applies to your scenario.
Are my inputs stored?
No. All calculations run client-side in your browser.

Resources and references

The formulas and methods in this calculator were checked against these independent sources.