Do CD rates change after you open the account?

Not on a standard fixed-rate CD — the rate you locked in at opening stays fixed for the entire term regardless of what happens to market rates elsewhere, since the fixed-rate guarantee is precisely the feature that makes the product different from a variable-rate account. What does change is the rate the bank offers to brand-new customers opening an account today, and separately, the rate your own CD will auto-renew into once it reaches maturity if you take no action. Suppose you locked a $10,000 CD at 4.50% APY, compounded daily, for a 12-month term: it matures at $10,450.00 regardless of whether the bank's advertised rate rises or falls to 5.00% or 4.00% during that year, since your contracted rate cannot move either way. At maturity, though, the bank's then-current standard rate applies to any renewal, which is a completely separate number from the rate you originally locked in and is worth checking before letting the CD roll over automatically.

Is a higher APY always the better CD?

Almost always, provided the term, minimum deposit, and your intended holding period all genuinely match, since APY alone measures the rate and says nothing about whether you can access it or would want to hold that long. The mechanism that trips people up is a rate you cannot actually qualify for, because it requires a jumbo minimum you cannot meet, or a term meaningfully longer than you need, which forces an early withdrawal penalty you had not planned on paying. Suppose Bank A offers 4.60% APY on a 5-year CD while Bank B offers 4.50% APY on a 12-month CD, and you actually need the money in 14 months: Bank A's higher headline APY would cost you an early withdrawal penalty to reach your money on schedule, while Bank B's slightly lower APY matures right on time with no penalty at all. The higher number only wins once the term and minimum are both ones you can genuinely use.

How do I convert a nominal interest rate to APY to compare it fairly?

Use the formula APY = (1 + r/n)^n − 1, where r is the nominal rate expressed as a decimal and n is the number of times per year the rate compounds, since this converts any bank's internal compounding schedule into the one standardized, annualized figure regulators require for comparison. A nominal rate alone tells you what the bank applies each period, not what you collect over a full year; the formula folds that missing compounding effect back in so the result is comparable to any other disclosed APY. Suppose Bank A quotes a nominal 4.30% rate compounded monthly: plugging r = 0.043 and n = 12 into the formula gives (1 + 0.043/12)^12 − 1 ≈ 0.043858, or about 4.3858% APY, which is the number you should actually set beside another bank's disclosed 4.50% APY rather than comparing the raw 4.30% nominal figure directly. On a $10,000 deposit for 12 months, that converted 4.3858% APY earns $438.58 in interest, matching Bank A's own monthly-compounding disclosure exactly.

Can I compare CD rates across different term lengths directly?

Yes, as APY figures, since APY is always annualized by regulatory definition regardless of the underlying term, so a 7-month CD's APY and a 12-month CD's APY sit on the same scale and can be compared directly. What trips people up is confusing that annualized rate with the total dollar amount collected, since a shorter CD only earns it for a fraction of the year, not the full twelve months the APY assumes. Suppose a 7-month CD advertises 4.60% APY and a 12-month CD advertises 4.50% APY on the same $10,000 deposit: the rates themselves are directly comparable as quoted, but the 7-month CD actually pays out roughly seven-twelfths of a full year's interest in dollar terms, while the 12-month CD collects a full year's worth, so the shorter CD's higher percentage does not mean a bigger total payout. Compare the APY percentages first, then apply your own term to see the actual dollar payout you would receive.

Why do online banks and credit unions often have better CD rates than large national banks?

Online banks avoid the cost of a branch network and compete for deposits primarily through the advertised rate, since without physical locations to draw customers in, a strong headline rate is one of the few tools they have. Credit unions operate under a different mechanism entirely: they are member-owned and not-for-profit, so any surplus the institution generates tends to flow back to members through better pricing on deposits and loans rather than out to shareholders as profit. Suppose a large national bank offers 3.50% APY on a 12-month CD while a comparable online bank offers 4.50% APY on the identical term: on a $10,000 deposit, the national bank earns $350.00 in interest for the year while the online bank earns $450.00, a $100.00 gap that reflects the overhead structure each institution is competing against, not any difference in deposit safety, since both remain equally FDIC-insured. Large national banks compete less aggressively on rate because they typically do not need the deposits as urgently to fund their lending.

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How to Find and Compare the Best CD Rates

快速存单计算器完整工具

到期时: US$10,450.00
利息: US$450.00

存款金额

利率 (APY)

存期

US$10,000.00 for 1 year, compounded daily. Runs in your browser.

Compare CD rates by converting every offer to APY, running each at your actual deposit and term, and reading the renewal terms. The headline rate alone is misleading because compounding frequency, term length and auto-renewal all change what you end up with.

发布于 2025年11月27日 · 最后核验 2026年7月22日 · 撰写与事实核查 Ali Raza · 我们的方法论 · 术语解释

Why the headline rate alone is not comparable

Two CD offers with the same advertised percentage can pay different dollar amounts, and two offers with different percentages can pay the same amount, because 'rate' is not one consistent thing across a rate sheet. It might be quoted as APY, which already includes compounding, or as a nominal rate, which does not. It might apply to your actual deposit, or only above a minimum tier the advertisement does not mention. And it might vanish at renewal, replaced by whatever the bank is offering new customers on that date.

Comparing headline numbers without controlling for these three variables — compounding basis, deposit tier, renewal terms — is the single most common reason savers pick the offer that looks best rather than the one that actually pays the most.

Step one: convert every quote to APY

If an offer is already labelled APY, it is ready to compare as-is. If it is labelled 'interest rate' or 'APR' with no further qualifier, convert it before it goes on your shortlist, using APY = (1 + r/n)^n − 1, where r is the nominal rate as a decimal and n is the number of compounding periods per year.

Skipping this step is where most rate-shopping mistakes happen: a 4.30% nominal rate compounded monthly and a 4.30% APY are not the same offer, and the gap between them widens as the compounding frequency and the rate itself increase. Converting everything to APY first means every later comparison in this process is apples to apples.

Why APY is comparable across different term lengths

A common hesitation is assuming you cannot compare a 7-month CD's rate against a 12-month CD's rate because the terms differ. You can, because APY is defined as an annualized figure by regulation regardless of how long the underlying term actually runs — a 7-month CD advertising 4.60% APY and a 12-month CD advertising 4.50% APY are directly comparable as rates, exactly as quoted.

What differs between the two is the total dollar amount you collect, since the shorter CD only earns that annualized rate for a fraction of the year. Do not mistake a CD's total percentage gain over its term for its APY — a CD that returns 4.60% APY over seven months does not hand you 4.60% of your deposit in cash at maturity; it hands you roughly seven-twelfths of that, because the rate itself, not the total payout, is the annualized figure.

A worked comparison: two banks, one true winner

Suppose Bank A quotes 4.30% as a nominal rate compounded monthly, and Bank B quotes 4.50% APY directly. Convert Bank A's figure first: APY = (1 + 0.043/12)^12 − 1 ≈ 4.3858%. On a $10,000 deposit over 12 months, Bank A's converted rate earns $438.58 in interest, matching its own monthly-compounding disclosure, and Bank B's daily-compounded 4.50% APY earns $450.00.

Before converting, Bank A's '4.30%' looked close enough to Bank B's '4.50%' that the 0.20-point headline gap might not have seemed worth the trouble of switching banks. After converting to a common basis, the true gap is 0.114 percentage points of APY, worth $11.42 over the year on this deposit, and proportionally the same on any balance.

Step two: check the minimum deposit tier

The advertised rate on a bank's page is often its top tier, available only above a stated balance, sometimes $10,000, sometimes the full jumbo minimum of $100,000. A tiered rate sheet might pay a full percentage point less at a $2,000 balance than at a $25,000 balance under the same headline number.

Always confirm which tier your actual deposit falls into before running any comparison. Comparing a top-tier rate against your real, smaller deposit at a competing bank is comparing an offer you cannot actually get against one you can, and it is a close second to skipping the APY conversion as the most common shopping error.

Step three: check whether the rate requires bundling

Some of the highest advertised CD rates are conditional on more than the deposit itself — opening a linked checking account, enrolling in paperless statements, or maintaining an existing relationship with the bank above a separate balance threshold. Miss one of these conditions and the CD can revert to a lower standard rate without much warning.

Read the fine print specifically for the phrase describing eligibility, not just the rate box. If a rate requires a bundle you were not planning to open anyway, price in the value of that bundle, or discount it entirely and compare against the bank's unconditional rate instead.

Step four: read the renewal terms before you fund anything

A rate that only applies for the current term is a rate you will need to re-evaluate at maturity, usually inside a grace period of about 7 to 10 days. Most CDs auto-renew into the bank's then-current standard rate for the same term if you take no action, and that standard rate is frequently well below the promotional rate that attracted the deposit in the first place.

A CD that wins the comparison today but renews poorly is only a win for one term. Diary the maturity date the day you open the account, and treat the renewal rate as part of the original decision rather than an afterthought you will deal with later.

Where the strongest rates usually sit

A few patterns hold consistently enough to be worth checking first:

Online banks, which carry no branch network and consistently pass that saved overhead through as a higher rate than large national banks with physical locations.
Credit unions, which are member-owned and not-for-profit, so surplus tends to return to members as rate rather than as profit; membership eligibility is often broader than it first appears.
Odd promotional terms — 7, 11, 13 months — priced aggressively specifically because they are hard to line up against a standard rate table.
Smaller or newer institutions actively trying to grow their deposit base, which sometimes out-pay larger, well-funded banks that do not currently need the money.

Common mistakes worth naming

A short list of the errors that recur across this entire process:

Comparing a nominal rate at one bank against an APY at another, without converting either to the same basis first.
Running the comparison at a round number like $10,000 when your actual deposit is smaller or larger, and missing that a tier boundary sits in between.
Confusing a CD's total dollar return over its specific term with its annualized APY, especially on odd terms shorter or longer than a year.
Ignoring the renewal rate entirely, so a strong first-term decision quietly turns into a mediocre standing arrangement two or three years later.

常见问题

Not on a standard fixed-rate CD — the rate you locked in at opening stays fixed for the entire term regardless of what happens to market rates elsewhere, since the fixed-rate guarantee is precisely the feature that makes the product different from a variable-rate account. What does change is the rate the bank offers to brand-new customers opening an account today, and separately, the rate your own CD will auto-renew into once it reaches maturity if you take no action. Suppose you locked a $10,000 CD at 4.50% APY, compounded daily, for a 12-month term: it matures at $10,450.00 regardless of whether the bank's advertised rate rises or falls to 5.00% or 4.00% during that year, since your contracted rate cannot move either way. At maturity, though, the bank's then-current standard rate applies to any renewal, which is a completely separate number from the rate you originally locked in and is worth checking before letting the CD roll over automatically.
Almost always, provided the term, minimum deposit, and your intended holding period all genuinely match, since APY alone measures the rate and says nothing about whether you can access it or would want to hold that long. The mechanism that trips people up is a rate you cannot actually qualify for, because it requires a jumbo minimum you cannot meet, or a term meaningfully longer than you need, which forces an early withdrawal penalty you had not planned on paying. Suppose Bank A offers 4.60% APY on a 5-year CD while Bank B offers 4.50% APY on a 12-month CD, and you actually need the money in 14 months: Bank A's higher headline APY would cost you an early withdrawal penalty to reach your money on schedule, while Bank B's slightly lower APY matures right on time with no penalty at all. The higher number only wins once the term and minimum are both ones you can genuinely use.
Use the formula APY = (1 + r/n)^n − 1, where r is the nominal rate expressed as a decimal and n is the number of times per year the rate compounds, since this converts any bank's internal compounding schedule into the one standardized, annualized figure regulators require for comparison. A nominal rate alone tells you what the bank applies each period, not what you collect over a full year; the formula folds that missing compounding effect back in so the result is comparable to any other disclosed APY. Suppose Bank A quotes a nominal 4.30% rate compounded monthly: plugging r = 0.043 and n = 12 into the formula gives (1 + 0.043/12)^12 − 1 ≈ 0.043858, or about 4.3858% APY, which is the number you should actually set beside another bank's disclosed 4.50% APY rather than comparing the raw 4.30% nominal figure directly. On a $10,000 deposit for 12 months, that converted 4.3858% APY earns $438.58 in interest, matching Bank A's own monthly-compounding disclosure exactly.
Yes, as APY figures, since APY is always annualized by regulatory definition regardless of the underlying term, so a 7-month CD's APY and a 12-month CD's APY sit on the same scale and can be compared directly. What trips people up is confusing that annualized rate with the total dollar amount collected, since a shorter CD only earns it for a fraction of the year, not the full twelve months the APY assumes. Suppose a 7-month CD advertises 4.60% APY and a 12-month CD advertises 4.50% APY on the same $10,000 deposit: the rates themselves are directly comparable as quoted, but the 7-month CD actually pays out roughly seven-twelfths of a full year's interest in dollar terms, while the 12-month CD collects a full year's worth, so the shorter CD's higher percentage does not mean a bigger total payout. Compare the APY percentages first, then apply your own term to see the actual dollar payout you would receive.
Online banks avoid the cost of a branch network and compete for deposits primarily through the advertised rate, since without physical locations to draw customers in, a strong headline rate is one of the few tools they have. Credit unions operate under a different mechanism entirely: they are member-owned and not-for-profit, so any surplus the institution generates tends to flow back to members through better pricing on deposits and loans rather than out to shareholders as profit. Suppose a large national bank offers 3.50% APY on a 12-month CD while a comparable online bank offers 4.50% APY on the identical term: on a $10,000 deposit, the national bank earns $350.00 in interest for the year while the online bank earns $450.00, a $100.00 gap that reflects the overhead structure each institution is competing against, not any difference in deposit safety, since both remain equally FDIC-insured. Large national banks compete less aggressively on rate because they typically do not need the deposits as urgently to fund their lending.

资料来源

上文所述的规则与限额均直接取自发布机构，而非二手转述。

Regulation DD, 12 CFR Part 1030 — Truth in Savings — CFPB
12 CFR 1030 Appendix A — Annual Percentage Yield calculation — CFPB
Federal Open Market Committee policy decisions — Federal Reserve