What is an effective annual rate?
It is the annual growth produced after applying the selected compounding frequency. Compare it with a quoted APY only when the compounding assumptions match.
Savings Interest Rate Calculator - Compound Earnings
Calculate simple or compound interest earnings for a principal, rate, term, and frequency.
Compare how compounding frequency and interest type affect a savings balance.
Interest assumptions
Enter the starting principal, stated annual rate, duration, compounding frequency, and interest type.
About savings interest earnings
Interest can be calculated in two fundamentally different ways. Simple interest applies the stated annual rate only to the original principal. Compound interest adds earned interest to the balance, allowing later interest periods to earn on earlier interest. The savings interest rate calculator shows future value and interest earned for either method, plus the effective annual rate for the selected compounding schedule. It is designed for a single starting deposit with no later contributions or withdrawals. Compounding frequency affects a compound balance when the stated nominal rate is held fixed. Monthly compounding credits interest twelve times each year, quarterly four times, and daily three hundred sixty-five times. More frequent compounding produces a slightly higher effective annual rate because interest begins earning interest sooner. The difference is usually modest at common savings rates, but it becomes clearer over longer periods or larger balances. Banks and investments may quote APY, APR, nominal annual rate, or effective annual rate. APY already reflects a stated compounding method, so do not compound it again as though it were nominal APR. Read the account disclosure for the actual balance method, rate tiers, minimums, withdrawal limitations, fees, and whether the rate can change. Certificates, bonds, money market accounts, and market investments can have different terms and risks. The estimate ignores taxes, fees, additional deposits, rate changes, and inflation. A balance that grows in dollars may have less buying power after inflation, and taxable interest may leave less cash than shown. For a savings goal with regular deposits, use a contribution projection instead. Use this calculation to compare known rate offers, check account statements, and understand the difference between simple and compound growth; it does not guarantee a future return. To compare offers fairly, use the same principal and time period for each account, then consider access to funds and the conditions required to earn the advertised rate. Some accounts tier rates by balance, limit transfers, require direct deposits, or reduce earnings after a promotional period. A certificate may state a fixed return but impose an early withdrawal penalty, while a variable savings account can change its rate. Daily compounding is not automatically better if the underlying annual rate is lower. Check statement dates and the bank’s day-count convention when reconciling a small difference from this estimate. For taxable accounts, compare the after-tax outcome as well as the published yield, particularly when choosing between alternatives with different tax treatment.
When comparing accounts, match the term and liquidity as well as the rate. A higher certificate rate may not compensate for an early-withdrawal penalty if the money could be needed before maturity, while a variable account can change its rate at any time.
Savings interest examples
These examples use monthly compound interest unless a different type is selected.
| Interest assumptions | Future value | Planning note |
|---|---|---|
| $10,000 at 5.25% for 5 years, monthly compound | $12,994.32 | Interest is added to the balance every month. |
| $10,000 at 5.25% for 1 year, monthly compound | $10,537.82 | One year of compounding adds $537.82. |
| $10,000 at 5.25% for 5 years, simple interest | $12,625.00 | Simple interest does not compound on prior interest. |
How to calculate savings interest and APY
- Enter the initial principal and stated annual rate.
- Choose the number of years.
- Select the account compounding frequency and interest type.
- Compare future value and effective annual rate with the account disclosure.
Savings interest rate FAQ
Should I enter APY or APR?
Use a nominal stated rate for this calculation; APY already includes a compounding effect. Entering APY as if it were a nominal rate would double-count compounding.
Why does simple interest differ?
Simple interest does not earn interest on previously earned interest. Over several years that usually produces a lower future value than monthly compounding.
Can I model monthly deposits?
The savings interest rate calculator models one principal deposit; use a savings projection for regular contributions. Monthly deposits need a future-value-of-annuity formula.