By Sang Lee — Founder and Editor of AssetCalculus
Quick answer: On a constant $10,000 balance held for one year, a 4.25% APY earns about $425, while a 4.00% APY earns about $400. The difference is $25 before taxes.
A quarter of a percentage point sounds small. On $10,000 for one year, it is small. But the difference grows with a larger balance, a longer holding period, or both. The important question is whether the higher APY comes with fees, balance limits, withdrawal restrictions, or requirements that erase the extra interest.
The One-Year Calculation
APY already reflects the effect of compounding over one year, assuming the stated rate remains available and the interest stays in the account. For a simple one-year comparison with no deposits or withdrawals:
Interest earned = Starting balance × APY
| Starting balance | 4.25% APY | 4.00% APY | Difference |
|---|---|---|---|
| $1,000 | $42.50 | $40.00 | $2.50 |
| $5,000 | $212.50 | $200.00 | $12.50 |
| $10,000 | $425.00 | $400.00 | $25.00 |
| $25,000 | $1,062.50 | $1,000.00 | $62.50 |
| $50,000 | $2,125.00 | $2,000.00 | $125.00 |
The shortcut is straightforward: a 0.25-percentage-point difference equals $2.50 per year for every $1,000 kept in the account, before taxes, if the balance and APYs remain unchanged.
What Happens Over Several Years?
If both APYs stayed constant and you left all interest in the account, compounding would gradually widen the gap. The formula is:
Ending balance = Principal × (1 + APY)years
| Time | 4.25% APY balance | 4.00% APY balance | Difference |
|---|---|---|---|
| 1 year | $10,425.00 | $10,400.00 | $25.00 |
| 5 years | $12,313.47 | $12,166.53 | $146.94 |
| 10 years | $15,162.14 | $14,802.44 | $359.70 |
These longer examples are mathematical illustrations. Savings-account APYs are variable and can change at any time. A certificate of deposit may offer a fixed APY for its term, but it can also impose an early-withdrawal penalty.
Why APY Is Better Than Comparing the Stated Interest Rate
The stated interest rate does not always show the full effect of compounding. APY is designed to make deposit accounts easier to compare because it incorporates compounding over a year. When comparing two savings accounts or CDs, use APY against APY—not an interest rate from one account against an APY from another.
If you want to model a starting balance, monthly contributions, rate, and time period, use the AssetCalculus Compound Interest Calculator.
Taxes Reduce the Difference
Interest from a bank account is generally taxable income. Suppose, only for illustration, that a saver’s combined applicable tax rate on the interest is 22%.
- 4.25% APY: $425 interest − $93.50 estimated tax = $331.50 after tax
- 4.00% APY: $400 interest − $88 estimated tax = $312 after tax
- After-tax difference: $19.50
Your actual federal and state tax treatment can differ. This is a mathematical example, not tax advice.
When the Higher APY Is Actually Better
The 4.25% account is the better numerical choice when both accounts have the same safety, access, fees, balance requirements, and rate stability. In real life, those conditions may not be equal.
- Monthly fees: A $5 monthly fee costs $60 per year, more than the $25 interest advantage on $10,000.
- Minimum balance: The advertised APY may require a particular balance.
- Balance cap: Some promotional APYs apply only to part of the account.
- Activity requirements: Direct deposit, debit transactions, or another linked product may be required.
- Withdrawal limits: A CD may charge a penalty for early access.
- Rate duration: A savings APY can change, while a CD rate may be fixed for a defined term.
- Deposit insurance: Confirm that the institution and account ownership category qualify for applicable FDIC or NCUA coverage.
Break-Even Test for Fees
On $10,000, the higher APY produces only $25 of additional first-year interest. Therefore, any extra annual cost above $25 eliminates the advantage.
For example, if the 4.25% account charges a $3 monthly fee, the yearly fee is $36. The account earns $25 more interest but costs $36 more, leaving it $11 behind before taxes.
What If the Balance Changes During the Year?
The simple $425-versus-$400 calculation assumes the full $10,000 remains in the account for the entire year. Deposits, withdrawals, changing APYs, and the timing of interest credits will change the result.
For monthly contributions, calculate each contribution for the number of months it remains invested. A deposit made near the end of the year cannot earn a full year of interest. This is why a calculator is more useful than the one-year shortcut when cash flows vary.
A Practical Decision Checklist
- Compare APY with APY.
- Verify whether the APY is variable, fixed, or promotional.
- Check monthly fees and waiver requirements.
- Check minimum balances and maximum qualifying balances.
- Review withdrawal rules and early-withdrawal penalties.
- Confirm deposit-insurance eligibility directly with the institution and the appropriate federal agency.
- Calculate the dollar difference using the balance you actually expect to keep.
Frequently Asked Questions
Is 0.25% APY a meaningful difference?
It depends on the balance and time period. It equals $25 per year on $10,000, $125 on $50,000, and $250 on $100,000 before taxes when balances and APYs remain constant.
Does 4.25% APY mean I receive 4.25% every month?
No. APY is an annualized yield. Interest may be calculated or credited more frequently, but 4.25% APY represents the approximate one-year yield under the account’s stated assumptions.
Can a savings account lower its APY?
Yes. Savings-account APYs are generally variable. The institution can change the rate, subject to applicable account terms and disclosure requirements.
Should I move $10,000 for an extra 0.25%?
Possibly, but first compare fees, transfer time, access, insurance coverage, service quality, and rate conditions. The maximum first-year advantage in this example is only $25 before taxes.
Where can I estimate other balances and time periods?
Use our Compound Interest Calculator. For a broader one-year explanation, see How Much Interest Does $10,000 Earn in a Year?
Bottom Line
At a constant $10,000 balance, 4.25% APY earns about $25 more than 4.00% APY over one year before taxes. The higher yield is worthwhile only when fees, restrictions, balance rules, and rate stability do not cost more than that advantage. Convert percentage differences into dollars before moving money.
Official Sources
- Consumer Financial Protection Bureau: Bank accounts
- Federal Deposit Insurance Corporation: Deposit insurance resources
- Investor.gov: Compound Interest Calculator
Educational purposes only. This article uses hypothetical rates that are not recommendations or current offers. Rates, fees, taxes, and account terms change. Verify details with the financial institution and a qualified professional when appropriate.