How to Calculate Interest Savings Account

What is Interest on a Savings Account?

Interest is the reward you earn for depositing money into a savings account. Banks pay this interest as compensation for lending your money to them. The amount of interest you earn depends on several factors, including the account balance, interest rate, and how often the interest is calculated and paid.

Savings accounts typically offer lower interest rates than other financial products like certificates of deposit (CDs) or money market accounts. However, they provide the flexibility to access your funds at any time without penalties.

How to Calculate Savings Interest

The basic formula for calculating simple interest on a savings account is:

Where:

• Principal is the initial amount of money deposited into the account.
• Rate is the annual interest rate (expressed as a decimal).
• Time is the number of years the money is saved.

For example, if you deposit $1,000 at a 2% annual interest rate for 3 years, your interest would be:

Most savings accounts use compound interest, which means the interest earned each period is added to the principal, and future interest is calculated on this new amount. The compound interest formula is:

Where:

• A is the amount of money accumulated after n years, including interest.
• P is the principal amount (the initial amount of money).
• r is the annual interest rate (decimal).
• n is the number of times that interest is compounded per year.
• t is the time the money is invested for, in years.

APR vs APY: What's the Difference?

When comparing savings accounts, you'll often see two types of interest rates: APR (Annual Percentage Rate) and APY (Annual Percentage Yield).

• APR is the simple interest rate that the bank advertises. It doesn't account for compounding.
• APY is the effective annual interest rate, which includes the effect of compounding interest. It gives a more accurate picture of the true return on your investment.

For example, if an account offers a 1% APR compounded monthly, the APY would be higher because the interest is compounded more frequently. The relationship between APR and APY is:

Where n is the number of compounding periods per year.

Understanding Compounding Interest

Compounding interest is when interest is calculated on the initial principal and also on the accumulated interest of previous periods. This can significantly increase your returns over time.

The more frequently interest is compounded, the higher your returns will be. Common compounding periods include:

• Annually (once per year)
• Semi-annually (twice per year)
• Quarterly (four times per year)
• Monthly (twelve times per year)
• Daily (365 times per year)

For example, $1,000 invested at 5% APR compounded annually for 10 years would grow to:

If the same amount were compounded monthly, the result would be:

Notice the difference of about $18 more with monthly compounding.

Example Calculation

Let's walk through a complete example to illustrate how to calculate savings interest.

Scenario

• Initial deposit (Principal): $2,500
• Annual interest rate (APR): 1.5%
• Compounding frequency: Monthly
• Time period: 5 years

Step 1: Convert the APR to a monthly rate

Step 2: Calculate the number of compounding periods

Step 3: Apply the compound interest formula

Step 4: Calculate the total interest earned

In this example, you would earn approximately $156.50 in interest over 5 years.