Interest is money the bank pays you for keeping your money there

When you deposit money into a savings account, the bank uses that money to lend to other customers. In exchange, the bank pays you interest — a percentage of your balance. That interest is usually calculated and added to your account once a month, though some banks do it daily or quarterly.

The amount you earn depends on three things: how much money you have in the account, what interest rate the bank is offering, and how long your money stays there. A higher balance earns more. A higher rate earns more. Money that sits untouched for the full month earns more than money you withdraw partway through.

Interest rates on savings accounts change. Banks raise them or lower them based on what the Federal Reserve does with its own rates. When the Fed raises rates, banks usually raise savings rates too — sometimes within days, sometimes over weeks. When the Fed cuts rates, savings rates typically fall.

Key Takeaways

  • Monthly interest is calculated as a percentage of your account balance and added once a month, though the exact day varies by bank.
  • The amount you earn each month depends on your balance, the bank's interest rate, and whether you add or withdraw money during the month.
  • Banks calculate interest using either a simple method (balance × rate ÷ 12) or a daily method (adding up each day's balance, then applying the rate).
  • Interest rates on savings accounts change when the Federal Reserve changes its rates, so your monthly earnings can go up or down.
  • You can compare rates across banks using rate-tracking websites, and switching to a higher-rate account can significantly increase your earnings over time.

How the bank calculates your monthly interest payment

Banks use one of two methods to figure out how much interest you've earned. The simpler method is called simple interest. The bank takes your balance at the end of the month, multiplies it by the annual interest rate, and divides by 12. If you have $5,000 and the rate is 4.5% per year, you earn about $18.75 that month ($5,000 × 0.045 ÷ 12).

The more common method is daily interest. The bank calculates what you've earned each day based on that day's balance, then adds all those daily amounts together at the end of the month. This method rewards you for money you deposit early in the month and penalizes you slightly for withdrawals. If you deposit $1,000 on the first day of a 30-day month at 4.5% annual rate, you earn more than if you deposit that same $1,000 on the 15th.

Your bank's account agreement or website will tell you which method they use. Most large banks and online banks use daily interest. Some smaller banks or older account types use simple interest.

When the interest actually hits your account

Interest is posted to your account on a statement date — usually the last day of the month, though some banks use the 25th or another fixed date. You can see the exact date in your account agreement or by looking at past statements. The interest appears as a deposit and increases your balance immediately.

Once interest is posted, it becomes part of your balance. The next month, you earn interest on the interest you earned the previous month. This is called compounding, and it means your money grows faster over time. With monthly compounding, a $10,000 balance at 4.5% annual rate grows to about $10,459 after one year, not $10,450.

Some banks post interest on different schedules. A few post quarterly (every three months) or annually (once a year). Check your account details to know when to expect your interest deposit. If you don't see interest posted when you expect it, contact the bank — it may have been delayed or the rate may have changed.

Why your monthly interest amount changes month to month

Even if the interest rate stays the same, the amount you earn each month can vary because your balance changes. If you deposit $2,000 partway through the month, you earn less that month than you would have if the full balance had been there the whole time. If you withdraw $3,000, your earnings drop. If you add money, your earnings go up.

The interest rate itself also changes. Banks adjust their rates regularly — sometimes weekly, sometimes monthly. When a rate goes up, your next month's interest payment will be larger. When a rate goes down, your payment shrinks. The Federal Reserve's decisions are the biggest driver of these changes, but individual banks also adjust based on competition and their own costs.

You can track your interest earnings by looking at your monthly statements. Each statement shows the interest posted that month and your new balance. Over time, you'll see the pattern: higher balance months earn more, and months when rates rise earn more than the months before.

How to find a savings account with a higher interest rate

Interest rates vary widely between banks. A large national bank might offer 0.01% on a basic savings account, while an online bank might offer 4.5% or higher on the same type of account. The difference is real money. On a $10,000 balance, 0.01% earns about $10 per year, while 4.5% earns about $450 per year.

You can compare rates using websites that track savings rates across banks. These sites update daily and let you filter by account type, minimum balance, and other features. You can also visit individual bank websites directly — most display their current rates on the homepage or in a rates section.

Online banks typically offer higher rates than brick-and-mortar banks because they have lower overhead costs. Credit unions sometimes offer competitive rates too, especially if you're a member. Before opening an account, check whether the bank is FDIC-insured (for banks) or NCUA-insured (for credit unions). This insurance protects your money up to $250,000 if the bank fails.

What happens if you move money between accounts

If you transfer money from one savings account to another, the interest calculation depends on when the transfer clears. Money that leaves your original account stops earning interest there once the transfer is complete. Money that arrives in your new account starts earning interest on the next statement date (or immediately, depending on the bank's rules).

Some banks have a grace period where they don't charge you for moving money between your own accounts. Others charge a fee for transfers to accounts at different banks. Check your account agreement before moving large amounts. If you're switching to a higher-rate account at a different bank, the fee might be worth it if you're moving a large balance, but it may not make sense for smaller amounts.

If you close an account before the statement date, the bank will still post any interest you've earned up to that point. You'll receive it as a final deposit before the account closes, or it may be mailed to you as a check.

How inflation affects what your interest earnings are actually worth

Interest earnings are real money, but their purchasing power depends on inflation. If your savings account earns 4.5% per year but inflation is running at 3%, your money is gaining real value at about 1.5% per year. If inflation is 5% and your rate is 4.5%, you're actually losing purchasing power even though your account balance is growing.

This matters most for money you're saving long-term. A high interest rate is valuable, but it's only part of the picture. You also want to know whether that rate will keep up with inflation over the time period you're saving. Checking current inflation rates and comparing them to current savings rates can help you decide whether a savings account is the right place for money you won't need for several years.

Frequently Asked Questions

Can I earn interest on interest in a savings account?

Yes. Once your monthly interest is posted to your account, it becomes part of your balance. The next month, you earn interest on that interest too. This is called compounding. The longer money sits in the account, the more powerful compounding becomes.

What if I withdraw money right before the interest posts?

If you withdraw money before the statement date, you lose interest on that amount for that month. The interest calculation is based on your balance on the statement date (or daily balances throughout the month, depending on the bank's method). Once you withdraw, that money no longer earns interest at that bank.

Do I have to pay taxes on savings account interest?

Yes. Interest earned on a savings account is taxable income. Banks send you a 1099-INT form at the end of the year if you earned $10 or more in interest. You report this on your tax return. The tax you owe depends on your total income and tax bracket.

Why do some banks offer much higher rates than others?

Online banks usually offer higher rates because they have lower operating costs than physical branches. They pass those savings to customers through better rates. Large national banks often offer lower rates because they spend more on branches, advertising, and staff. Credit unions may offer competitive rates to members.

If I move my money to a higher-rate account, will I lose the interest I already earned?

No. Interest that has already been posted to your account is yours to keep. When you transfer money to a new account, you take that balance with you. You only stop earning interest at the old bank once the transfer is complete.