Key Takeaways
- APY is an effective annual yield, so the monthly equivalent is the twelfth root, not a division by twelve. A 4.00% APY grows a balance by exactly 4.00% over a year, by definition.
- A flat monthly fee is a percentage on a small balance. Five dollars a month is 6% a year on $1,000 and 0.06% on $100,000, so the same account is a different product at different balances.
- A minimum balance to earn the advertised rate creates two rates, and an account can sit under the threshold for part of the period and over it for the rest.
- The account with the highest headline rate often does not finish with the most money. The calculator flags that case explicitly, because it is the finding the tool exists to produce.
- Rates on deposit accounts are variable and can change at any time. Every rate here is a value the reader supplies, not a quoted or tracked figure.
- Deposit insurance is not a return, but it is the reason the balance cannot fall. Insurance coverage rules are separate from the arithmetic here.
What Does APY Actually Mean?
Annual percentage yield is the effective annual rate of return, including the effect of compounding, on a deposit account. It is defined and its calculation is specified in the federal rules governing deposit account disclosures, which is why APY is directly comparable across institutions in a way a stated interest rate is not.
The consequence that matters for a comparison tool is arithmetic. Because APY already includes compounding, converting it into a monthly rate means taking the twelfth root, not dividing by twelve:
monthly rate = (1 + APY)^(1/12) − 1
Dividing by twelve is the correct treatment for an APR on a loan, where the stated rate is nominal and the compounding is applied on top. Doing it to an APY double-counts the compounding and overstates the ending balance. This calculator takes the twelfth root, which is why $10,000 at a 4% APY comes back at $10,400.01 after twelve months and not at something slightly higher.
That property is worth using as a check. If a deposit calculator turns a 4% APY into meaningfully more than 4% over one year, it is applying the wrong conversion.
Why a Flat Fee Beats a Rate Difference on Small Balances
A rate is a percentage of the balance. A maintenance fee is a fixed number of dollars. The two scale in opposite directions, and on small balances the fixed number wins easily.
Take a $5 monthly fee. Over a year that is $60. On a $1,000 balance, $60 is 6%. No realistic APY advantage covers a 6% drag, which means an account charging that fee is simply the wrong account at that balance regardless of its rate. On a $100,000 balance the same $60 is 0.06%, at which point a rate advantage of a quarter of a percent comfortably outweighs it.
This is why fee waivers are structured the way they are, typically conditional on a minimum balance, a direct deposit or a number of transactions. The waiver conditions are the actual product terms; the advertised rate is the headline. The Consumer Financial Protection Bureau's material on fees appearing on nominally free accounts makes the same point about conditions attached to accounts marketed on their absence.
The calculator reports the fee expressed as an annual percentage of the starting balance for each account, which converts the dollar figure into something directly comparable against the APY it is being weighed against. When that number is larger than the rate difference between two accounts, the fee has decided the comparison.
Savings Account Comparison
Enter up to four accounts. Every rate and fee is a figure you supply from the account disclosures in front of you. Nothing here tracks or quotes a live rate.
Illustrative arithmetic on the figures entered above. Deposit rates are variable and can change at any time, so a comparison run today may not describe the same accounts next month. Interest posts monthly, then the fee, then the deposit. Tax on interest is not modelled, and this is not a recommendation of any account or institution.
The comparison
Account by account
| Rank | Account | APY | Interest earned | Fees paid | Net gain | Ending balance | Behind the best by |
|---|
What the fee costs as a rate
| Account | Monthly fee | Fee per year as a percentage of the starting balance | Months spent below the minimum |
|---|
The fee column is the number to compare against an APY difference. When it is larger than the gap between two rates, the fee has decided the comparison.
Worked Example: The Higher Rate Loses
Three accounts, $10,000 deposited, twelve months, no monthly additions.
- Online savings: 4.00% APY, no monthly fee.
- Bank savings: 4.50% APY, $5 monthly fee.
- Legacy account: 0.50% APY, no monthly fee.
Online savings. The monthly rate is 1.04^(1/12) − 1, which is 0.32737%. Compounded for twelve months on $10,000, the balance ends at $10,400.01. The one cent above $10,400.00 is rounding to the nearest cent each month, and it is the check that the APY conversion is right.
Bank savings. The higher rate earns $448.76 of interest over the year, but $60 of fees comes out, so the balance ends at $10,388.76.
Legacy account. $50 of interest, no fees, ending at $10,050.00.
The account with the highest advertised rate finishes second. The half-point rate advantage is worth $48.75 over the year and the fee costs $60, so the fee wins by $11.25. The calculator flags this case explicitly because it is not visible from the rates alone.
Change one thing and the answer flips. At a $50,000 starting balance the rate advantage is worth roughly five times as much while the fee stays at $60, and the higher-rate account wins comfortably. The same two accounts, ranked differently, purely because of the balance. That is the reason a comparison has to be run on your own numbers rather than read off a table of rates.
Common Mistakes and Misconceptions
- Comparing on rate alone. The rate is one of at least three terms. On small balances it is frequently the least important of them.
- Confusing APY with interest rate. APY includes compounding and a stated interest rate does not, so the two are not interchangeable and dividing an APY by twelve overstates monthly growth.
- Ignoring the fee waiver conditions. A fee waived on a minimum balance or a direct deposit is waived only while that condition holds. The condition is the product term, not a footnote.
- Assuming the rate is fixed. Deposit account rates are variable and change without a term ending. A comparison run today describes today, which is why a certificate of deposit, with a rate fixed for a term, is a different kind of instrument.
- Forgetting tax. Interest on a taxable account is generally taxable income, which reduces the effective return. This calculator does not deduct it.
- Chasing a rate difference worth less than the switching effort. Running the comparison shows the annual gap in dollars, which is the honest measure of whether moving is worth doing.
What This Calculator Does Not Model
- Any live rate. Nothing here tracks, quotes or recommends an account. Every figure is entered by the reader from disclosures they are looking at.
- Fee waiver conditions. The fee entered applies every month. An account whose fee is waived above a balance can be modelled by entering zero, but the calculator will not switch between the two states.
- Introductory and tiered rates. One rate applies above the minimum and one below it. A promotional rate for the first few months, or a schedule of tiers by balance band, is outside the model.
- Transaction limits and penalties. Withdrawal restrictions, excess transaction fees and early withdrawal penalties on term products are not modelled.
- Tax. Interest is credited gross. Tax treatment depends on circumstances and account type.
- Deposit insurance limits. Coverage depends on ownership category and institution, and a balance above a coverage limit is a real consideration that no rate comparison addresses.
What the Comparison Cannot Tell You
The arithmetic ranks accounts on ending balance, which is one input into a decision rather than the decision itself. Four things sit outside it and are worth weighing deliberately.
Whether the money is insured, and up to what. A deposit account at an insured institution is protected up to the applicable limit per depositor, per institution, per ownership category. That protection is why a deposit account is the right home for money with a fixed date and a fixed amount, and it is not a return, so it never appears in a ranking by ending balance. A balance approaching a coverage limit is a reason to split across institutions regardless of which one pays the better rate.
Whether the rate will still be there. Deposit rates are variable. An account leading a comparison today can be repriced next month, and accounts that lead on rate are sometimes the quickest to reprice. Where a rate needs to be certain for a known period, a certificate of deposit fixes it for a term at the cost of access, and the CD ladder builder on this site handles the structure that trades those against each other.
Whether the access matches the purpose. An emergency reserve needs to be reachable the day it is needed, which rules out anything with a notice period or a withdrawal penalty however good the rate. A sinking fund for a bill eleven months away does not have that constraint. The right account depends on what the money is for, and the ranking here does not know.
Whether the difference justifies the switching. The calculator reports the gap between the best and worst accounts in dollars over the period entered. That figure is the honest measure of what moving is worth. Where it comes back at a few dollars a year, the effort of opening an account, moving direct deposits and updating transfers is very likely worth more than the gap. Where it comes back at several hundred, it is not close.
The most durable finding from running this comparison is usually not which account wins but how much the answer depends on the balance. A fee-charging account with a strong rate is a good account for a large balance and a bad one for a small balance, and the same account can be both as a balance grows. That is worth re-checking when a balance changes materially, rather than treating an account choice made at one balance as settled forever.
Frequently Asked Questions
What is the difference between APY and an interest rate?
An interest rate is the nominal rate before compounding is applied; APY is the effective annual yield after compounding is included. Because APY already contains the compounding effect, it is directly comparable across accounts that compound on different schedules, which is why deposit disclosures are built around it. Converting an APY to a monthly figure means taking the twelfth root, not dividing by twelve.
How do I convert an APY into a monthly rate?
Take the twelfth root: monthly rate = (1 + APY)^(1/12) - 1. A 4.00% APY becomes a monthly rate of about 0.32737%, and compounding that for twelve months grows a balance by exactly 4.00%. Dividing the APY by twelve instead is the treatment for a nominal APR on a loan, and applying it to an APY double-counts the compounding and overstates the result.
Does a higher APY always mean more money at the end?
No, and this calculator flags the cases where it does not. A flat monthly maintenance fee is subtracted in dollars rather than percent, so on a small balance it can easily exceed a rate advantage. In the worked example on this page, an account paying 4.50% with a $5 monthly fee finishes $11.25 behind one paying 4.00% with no fee on a $10,000 balance over twelve months.
How much does a monthly maintenance fee really cost?
It depends entirely on the balance, which is the point. A $5 monthly fee is $60 a year, which is 6% of a $1,000 balance, 0.6% of a $10,000 balance and 0.06% of a $100,000 balance. The calculator reports each account’s fee as an annual percentage of the starting balance so it can be compared directly against the APY difference it is being weighed against.
What happens if my balance drops below the minimum for the advertised rate?
The account earns the lower rate for any month in which the balance is under the threshold. This calculator checks the balance at the start of each month and applies whichever rate applies, then reports how many months were spent below the minimum. An account can sit under the threshold early in a period and over it later as deposits accumulate.
Are the rates in this calculator real?
No. Every APY, fee and minimum balance is a value you enter from the disclosures of accounts you are actually looking at. Swoopr Investment does not track, quote, rank or recommend any bank, credit union or account, receives no compensation from any institution, and states no rate or fee as a current market fact anywhere on this page.
Does this calculator include tax on the interest?
No. Interest is credited gross, so the figures shown are before any tax. Interest on a taxable deposit account is generally taxable income, which reduces the effective return and can change a close comparison. Tax treatment depends on the account type and on individual circumstances, and is outside what this arithmetic models.
Is a savings account or a CD better for money I need on a specific date?
They trade different things. A savings account keeps the money accessible but its rate is variable and can change at any time. A certificate of deposit fixes the rate for a term, which removes that uncertainty, at the cost of an early withdrawal penalty if the money is needed sooner. Where the date is known and firm, a term matched to it removes one variable; where access might be needed, it does not.
How does deposit insurance affect this comparison?
It does not appear in the arithmetic at all, because it is protection rather than a return, but it is the reason a deposit account is a suitable home for money with a fixed date. Coverage applies up to a limit per depositor, per insured institution, per ownership category. A balance approaching that limit is a reason to split across institutions regardless of which one pays the better rate.
Is anything I enter sent anywhere?
No. The whole comparison runs in the browser on the numbers typed into the form. Nothing is transmitted to Swoopr Investment, to any bank or to any third party, nothing is stored between visits, and no account is opened or contacted. The calculator never asks for and must never be given an account number.
References
- CFPB: Regulation DD, Appendix A, Annual Percentage Yield Calculation
- CFPB: Regulation DD, 12 CFR 1030.2, Definitions
- CFPB: Fees Charged on a Free Checking Account
- CFPB: What Is a Money Market Account?
- CFPB: How Can I Be Sure My Money Is Safe in My Bank Account?
- FDIC: Understanding Deposit Insurance
- CFPB: What Is a Certificate of Deposit (CD)?
Every source above was retrieved and its document title confirmed on 23 August 2026. Rules, disclosure requirements and product terms change, so a figure taken from any of them should be re-checked against the current version before it is relied on. Swoopr Investment quotes no rate, fee or product term as a current fact anywhere on this page: every rate, fee and term in the calculator is a value the reader supplies.