How Banks Calculate Interest on Savings Accounts Explained

Banks calculate savings-account interest with a mathematical formula that uses your account balance, interest rate and how long the money has been in your account. Most accounts have an additional variable: how frequently interest is compounded.

The annual percentage yields (APYs) banks publish account for both the interest rate and the compounding, so APY is the best measure for rates.

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Key Takeaways

• Banks calculate savings interest from your balance, rate, compounding frequency and time. More frequent compounding — daily versus monthly — earns you slightly more over the same period.

• APY is the number to compare, not the interest rate. Because APY folds in compounding, two accounts with the same rate can pay different amounts.

• The federal funds rate steers savings rates, but each bank sets its own. When the Fed's target range moves, savings APYs usually follow, though banks adjust based on their own priorities.

• Where you bank shapes your rate as much as the Fed does. Online banks and credit unions often pay far more than the roughly 0.38% national average, with high-yield accounts reaching 4% or more.

Summary generated by AI, verified by MoneyLion editors

What Determines Your Savings Account Interest Rate?

These are the factors that influence your savings account interest rate.

• Federal funds rate: The Federal Open Market Committee (FOMC) sets a target range for the federal funds rate. It's based on factors like the strength of the economy, inflation and employment. Banks use that range as a guide when they lend money to each other overnight. As the federal funds rate goes up or down, interest rates on savings accounts usually follow suit.

• Business considerations: Banks set their rates based on supply and demand for their products and their strategic and financial priorities. For example, they might increase the rate on a certain account to encourage more people to open it, or decrease a rate to shift interest away from a product.

• Type of financial institution: Brick-and-mortar banks usually offer the lowest rates because they have high overhead, and they prioritize profits. Online banks have low overhead, so their rates are often higher. Credit unions, which are not-for-profit and member-owned, prioritize value for their members, and their rates are often competitive. 

• Type of savings account: The average rate for savings accounts was just 0.38% as of June 15, and many standard savings accounts pay much less. However, rates on high-yield savings accounts can reach 4% or higher. Money market accounts may also have higher-than-average rates.

• Account balance: Banks sometimes set tiered rates based on your account balance. That can work in your favor if rates increase with your balance. It might work against you if higher balances earn lower rates.  

• Compounding frequency: Compound interest is the money you earn on your deposits plus any interest those deposits have earned. Compounding accelerates your interest earnings, and more frequent compounding — daily vs. monthly, for example — maximizes that acceleration and your APY.

Simple Interest vs. Compound Interest: What’s the Difference?

• Simple interest is the interest earned on your deposits.

• Compound interest is the interest earned on your deposits and all the interest your deposits have earned.

The distinction is important because compound interest keeps your balance growing even if you stop making deposits into the account. Here's how they work:

The rate is important with both types of interest, but APY is the best way to compare rates for different accounts because it accounts for compounding.

• Two accounts with the same rate will have different APYs if one earns simple interest and the other earns compound interest. One account compounds interest more frequently than the other.

How To Calculate Your Savings Account Interest

Your bank statements tell you how much interest you’ve earned. But if you like a good math challenge, you can calculate your interest manually. 

To keep it simple, say you made a single $2,000 deposit three years ago. The interest has been 2% APY the entire time — a purely hypothetical rate for illustrative purposes. Your bank compounded interest one time each year. Your interest is $122.42.

The formula to make this calculation is A = P(1 + r/n)nt 

Here’s how to apply it:

• Note your principal — $2,000 in this example.

• Divide the percentage rate by 100 to convert it to a decimal — 2/100 = 0.02.

• Note the compounding frequency per year.

• Note the number of years — 3 for this example.

• Enter the numbers into the formula — A = 2000(1 + 0.02/1)^(1x3).

• Subtract the principal from A — $2,122.42 − $2,000 = $122.42.

Again, this is a simplified example. Most bank accounts compound interest daily, not annually, and they usually apply it to your account once per month. 

How Much Can Your Savings Actually Earn?

How much your savings can earn depends on your initial balance and additional deposits, the interest rate, compounding frequency and length of time the money is allowed to grow. Here are some examples.

As you can see, the higher the rate and the longer you keep your money saved, the faster the balance grows, even if you never make another deposit — hence the phrase, “magic of compound interest.”

Building a regular savings habit supercharges that growth.

Are Savings Accounts Worth It, or Should You Diversify?

Starting a savings account can be a safe way to grow your money. As long as your financial institution is insured by the Federal Deposit Insurance Corporation (FDIC) or National Credit Union Administration (NCUA), your principal is protected up to $250,000 per depositor, per insured institution, for each ownership category.

However, inflation can offset some or all of your interest and chip away at your principal’s purchasing power. And even under the best circumstances, yields are lower than you might earn with stocks or other long-term investments. 

What a Savings Account Is Best For

• Build an emergency fund

• Save for a major purchase in the next few years

• Create a "sinking fund" for a special purpose, like an annual vacation or quarterly bills

• Keep easy access to your extra cash

Keep In Mind

Some banks charge maintenance and other fees, such as excessive-withdrawal fees for making more withdrawals in a statement period than the account allows. Be sure to read the account deposit agreement and fee schedule before you sign up.

The Bottom Line

• The federal funds rate influences your interest rate, but banks set their own rates and APYs.

• Banks calculate interest based on your account balance, interest rate, compounding frequency and how long your funds have been in your account.

• APY is a more accurate measure than interest rate when you’re comparing accounts. That’s because APY accounts for compounded interest.

• A savings account is a great way to save for emergencies and short- and medium-term financial goals, but diversification will help maximize long-term growth.

Savings Account Interest FAQs

Here’s some more information about savings account interest.

How much interest would $1,000 make in a savings account in one year?

How much $1,000 will make in a savings account in one year will depend on the interest rate. With a high-yield savings account with a 3.4% interest rate, $1,000 will make $34 in one year.

How do you calculate the total interest on a savings account?

To find simple interest on a savings account in a set period, the formula is:

• Interest = principal (beginning balance) x interest rate x number of time periods

For example, for $1,000 in principal in a savings account paying 4% per year, you can write:

• $1,000 x .04 x 1 = $40 to find the interest earned after one year

Does my bank compound interest monthly or annually?

You’ll have to check your deposit account agreement and fee schedule or contact your bank to find out for sure. But most banks compound interest daily and credit it to your account monthly.

Is a high-yield savings account better than a regular savings account?

All else, such as fees and account restrictions, being equal, a high-yield account is better because it grows your money faster.

Does the Federal Reserve affect my savings account interest rate?

The federal funds rate influences savings account interest rates. But banks set their own rates. 

Do savings accounts pay interest every month?

Most, but not all, do. Check your deposit account agreement and fee schedule or contact your bank to find out how often it credits interest to your account.

Key Terms

• APY: The yearly rate you earn on savings, including the effect of compounding. It's the most accurate way to compare accounts because it reflects both the interest rate and how often interest compounds.

• Interest rate: The base rate a bank pays on your balance, before compounding is factored in. Two accounts with the same rate can still earn different amounts depending on compounding.

• Simple interest: Interest earned only on your original deposit — the principal. It doesn't grow on previously earned interest.

• Compound interest: Interest earned on both your deposits and the interest they've already earned. More frequent compounding accelerates growth, even if you stop adding money.

• Compounding frequency: How often a bank calculates and adds interest to your balance — daily, monthly or annually. More frequent compounding raises your effective APY.

• Federal funds rate: The target range the FOMC sets for overnight lending between banks. It heavily influences the direction of savings account rates.

• High-yield savings account: A savings account, often from an online bank, that pays a much higher APY than a standard account thanks to lower overhead.

Summary generated by AI, verified by MoneyLion editors

Sources

• Consumer Financial Protection Bureau. 2023. "How does compound interest work?"

• FDIC. 2026. "National Rates and Rate Caps – June 2026."

• 1st Franklin Financial. 2026. "What Is Simple Interest? A Complete Guide with Formula & Examples."

• Citizens Bank. "How to calculate compound interest."

• Fidelity. 2025. "What is APY and how is it calculated?"

Alison Kimberly contributed to the reporting for this article.

Information is accurate as of July 17, 2026.