CD Promotion Calculator
A promotional CD rate is a headline with an expiry date. The deposit earns the featured rate for a few months, then drops to the standard rate for the rest of the term, and judging the offer on the headline alone overstates what you actually earn. This calculator splits any two-rate CD promotion into its two periods and shows what each part pays, at any bank or credit union.
Enter the deposit, both rates, the promotional months, and the total term. You get the promotional interest, the standard-period interest, the total, and the final balance, so the blended return is visible before you commit any money. This page is not affiliated with any bank, and it holds no bank’s live rates: every rate is one you type in from an offer you are checking.
Pre-filled with the worked example from this page: $10,000 at 5 percent for 6 promotional months, then 4 percent for the remaining 6 months of a 12 month term. Estimate uses daily compounding in each period; see the compounding note in the article.
Quick Answer
Key takeaways
- Judge a promotion on the blended return across the full term, never the headline rate.
- The standard period earns on the grown balance, so it pays slightly more than a flat-rate guess.
- This estimate compounds interest daily in both periods, matching how Citi CDs compound, so each period earns interest on interest as well as on the deposit.
- Verify the exact bank named on the offer, and price renewal and penalty terms before you commit.
- Quick Answer
- How to use this promotion calculator
- The math of a two-rate CD, period by period
- What competing calculators miss
- An honesty note: daily compounding, the way real CDs pay
- Before you chase a headline rate: renewal, penalties, and tiers
- Frequently Asked Questions
- Add This Calculator to Your Website
- References
How to use this promotion calculator
Read the offer terms first, then mirror them here. The five inputs map one-to-one onto the language of a CD promotion, whichever bank issued it.
Run the same deposit through a plain savings comparison, such as the high-yield savings calculator, before locking money away; flexibility sometimes beats a locked promo.
The math of a two-rate CD, period by period
Each period compounds daily: balance = principal x (1 + rate / 365)365 x years. Period one: $10,000 x (1 + 0.05 / 365)365 x 0.5 grows to $10,253.13, so the promo interest is $253.13. Period two compounds on that grown balance: $10,253.13 x (1 + 0.04 / 365)365 x 0.5 reaches $10,460.25, so the standard interest is $207.12. Total interest is $460.25 and the final amount is $10,460.25.
The detail most promo pages skip: the standard period earns on the deposit plus the promo interest, not on the deposit alone, and each period also earns interest on its own interest as the days pass. That is why the standard line reads $207.12 rather than a flat $200.00, and why the blended rate, about 4.60 percent, sits slightly above the simple average of the two rates. Anyone sketching this on paper with the annual interest to monthly calculator will land on the same split. To explore daily compounding on a single rate over other terms, run the same deposit through the daily compound calculator.
| Scenario | Promo interest | Standard interest | Total | Final amount |
|---|---|---|---|---|
| Worked example: 5% for 6 mo, then 4% | $253.13 | $207.12 | $460.25 | $10,460.25 |
| Standard rate only, 4% all year | $0.00 | $408.08 | $408.08 | $10,408.08 |
| Promo rate all year, 5% (rare) | $512.67 | $0.00 | $512.67 | $10,512.67 |
| Shorter promo: 5% for 3 mo, then 4% | $125.78 | $308.36 | $434.13 | $10,434.13 |
| Larger deposit: $25,000, 5.25% for 6 mo, then 4.10%, 18 mo term | $664.89 | $1,074.07 | $1,738.96 | $26,738.96 |
The table makes the promotion’s real value plain: against a plain 4 percent CD, this offer is worth an extra $52.17 over the year on $10,000. Worth having, but not the $100 the headline gap suggests.
What competing calculators miss
Generic CD calculators take one rate and one term, which makes a two-rate promotion impossible to model without hand-editing halfway through. Bank and rate sites pair a single-rate tool with live rate tables, which is useful for shopping but still cannot price a step-down inside one term. Ladder calculators blend rates across separate CDs, not across two periods of the same CD. None of them show the standard period earning on the grown balance. This calculator is built around the split itself: five inputs that mirror the offer’s own wording, both periods priced separately, the blend made explicit, and daily compounding applied inside both periods instead of a simple-interest shortcut.
An honesty note: daily compounding, the way real CDs pay
This tool compounds interest daily inside each period, using balance = principal x (1 + rate / 365)365 x years, because that is how real CDs pay. Citibank states it directly on its Certificates of Deposit page: interest on CDs is compounded daily, and its account disclosures add that interest is compounded daily for the actual number of days the money is on deposit, using the daily balance method. Daily compounding is also why each line here sits a little above a simple-interest figure: the promo period pays $253.13 instead of $250.00 on the worked example.
Read the result as a close estimate, not a quote. The tool uses a 365-day year throughout, while a bank counts the actual days on deposit and may use a 366-day basis in a leap year, and crediting choices, such as sending interest to another account instead of leaving it in the CD, change the payout. For the exact maturity value, the bank’s own disclosure and APY govern. APY itself is the legally standardized figure that already folds compounding in, which is why offers must be compared APY to APY, never rate to APY. The U.S. Securities and Exchange Commission’s investor site makes the same point about high-yield CD offers: read the disclosure, confirm the issuer, and check the fine print before the rate.
Before you chase a headline rate: renewal, penalties, and tiers
Three traps decide whether a promotion is worth taking, and none of them is the headline rate. Automatic renewal: a CD that matures usually rolls into a new term at the then-current standard rate unless you act inside the grace period, which is commonly around seven days, so the promo you priced may quietly become a plain CD. Early withdrawal penalties: published terms at many banks charge around 90 days of simple interest on terms of a year or less and 180 days on longer terms, enough to erase a promotion’s edge if you break the CD. Rate tiers: featured rates may depend on balance size and relationship status, so the rate you qualify for may not be the rate in the advertisement.
One more check costs nothing: confirm the exact institution named on the offer. Rate roundups routinely mix up similarly named banks, and promotions, minimums, and penalties differ between them, so verify the issuer before typing rates into any calculator, including this one. The CD ratio calculator covers a different topic entirely, the banking liquidity ratio, and is a good reminder of how many unrelated ideas share the CD abbreviation.
Checking a Citi offer specifically? This page used to carry Citibank in its name, but it never held Citi rates: every number was always typed in by the reader. For Citibank’s current featured and standard CD terms, use Citibank’s official Certificates of Deposit page, then bring the two rates back here to price the step-down. Calculator Zilo is not affiliated with Citibank or Citigroup.
Frequently Asked Questions
The deposit earns the promotional rate for the promotional months, then the standard rate for the rest of the term. This calculator splits the term at exactly that point: promo interest first, compounded daily, then standard interest, also compounded daily, on the grown balance, then the two added together.
It is the single rate that would have produced the same total interest over the full term. In the worked example the blend of 5 percent for 6 months and 4 percent for 6 months works out to about 4.60 percent, because the second period also earns interest on the first period’s interest, and daily compounding inside each period adds a little more.
Yes. The tool compounds interest daily within each period, the same method Citibank discloses for its CDs: interest on CDs is compounded daily. The standard period then compounds on the balance the promo period grew to. Treat the result as a close estimate, not a payout quote, because a bank counts the actual days on deposit and may use a 366-day basis in a leap year, while this tool uses 365 days throughout.
Yes, with one setting. Set the promotional months equal to the total term and enter your rate as the promotional rate. The standard period becomes zero months, the standard interest line reads zero, and the result is a plain single-rate estimate with daily compounding, the same method the tool uses for both periods of a promotion.
Nothing changes about the account itself; only the rate steps down to the standard rate for the remaining months. The step-down is the whole point of modeling it: a headline promo rate overstates the full-term return unless the standard period is counted too.
On the bank’s own certificate of deposit page, not in a roundup. This calculator holds no live rates for any bank. If your offer is from Citibank, its official Certificates of Deposit page lists the current featured and standard terms; bring those two rates back here to price the promotion. Calculator Zilo is not affiliated with Citibank or any other bank.
Interest is taxable income in the year it is credited, reported on Form 1099-INT. Deposits at an FDIC-insured bank are insured up to $250,000 per depositor, per bank, per ownership category, including accrued interest; credit union share certificates carry the same limit through the NCUA.
Add This Calculator to Your Website
References
- Citibank, “Certificates of Deposit”: current featured and standard CD terms, minimum deposits, grace period, and renewal terms, straight from the issuing bank, for readers pricing a Citi offer; also the source for the statement that interest on CDs is compounded daily. Citibank: Certificates of Deposit. Accessed October 2026.
- Federal Deposit Insurance Corporation, “Deposit Insurance”: deposits are insured to at least $250,000 at each FDIC-insured bank, the coverage behind the $250,000 per depositor, per bank, per ownership category limit that applies to CDs. FDIC: Deposit Insurance. Accessed October 2026.
- Federal Deposit Insurance Corporation, “National Rates and Rate Caps”: the national average CD rates used to judge whether a featured rate is genuinely above market. FDIC: National Rates and Rate Caps. Accessed October 2026.
- Consumer Financial Protection Bureau, “What is a certificate of deposit (CD)?”: plain-language guidance on how CDs work, and on comparing term, interest rate, and the penalty for withdrawing money early. CFPB: What Is a Certificate of Deposit (CD)?. Accessed October 2026.
- Internal Revenue Service, “Topic No. 403, Interest Received”: CD interest is taxable income reported on Form 1099-INT. IRS: Topic No. 403, Interest Received. Accessed October 2026.
- Internal Revenue Service, “Publication 550, Investment Income and Expenses”: how CD interest is reported each year and how early withdrawal penalties are deducted. IRS: Publication 550, Investment Income and Expenses. Accessed October 2026.
- Consumer Financial Protection Bureau, “Regulation DD, Truth in Savings (12 CFR Part 1030)”: the federal rule that standardizes APY disclosure so offers can be compared fairly. CFPB: Regulation DD, 12 CFR Part 1030. Accessed October 2026.
- U.S. Securities and Exchange Commission, Investor.gov, “High-Yield CDs: Protect Your Money by Checking the Fine Print”: confirming the issuer, reading disclosures, and checking deposit insurance before chasing a featured rate. Investor.gov: High-Yield CDs, Protect Your Money by Checking the Fine Print. Accessed October 2026.
- U.S. Securities and Exchange Commission, Investor.gov, “Brokered CDs: Investor Bulletin”: how brokered CDs differ from bank CDs on insurance aggregation and early exit. Investor.gov: Brokered CDs, Investor Bulletin. Accessed October 2026.