The Safest Money Still Deserves Real Math
A certificate of deposit won’t make you rich — but in a high-rate environment, the difference between a 4.5% CD compounded daily and a 5% CD compounded annually is real money, and most savers never compute it. Worse, many compare CDs by APR (the stated rate) instead of APY (the true yearly return after compounding) — the number that actually decides which CD pays more.
This free CD calculator projects your deposit to maturity with any compounding frequency, shows the interest earned year by year, converts APR to true APY, and reveals exactly how much compounding adds over simple interest.
Certificate of deposit · APY · compounding
Please enter a deposit above $0, a rate of 0–100%, and a term of at least 3 months.
Value at maturity
After the full term
APY (annual percentage yield) is the true yearly return after compounding — always compare CDs by APY, not APR. Early withdrawal usually forfeits several months of interest, so only lock up money you won’t need. Most US bank CDs are FDIC-insured up to the legal limit. Educational math, not financial advice.
How to Use This Calculator
- Enter your deposit — the amount going into the CD.
- Enter the APR (the bank’s stated annual rate) and the term in years.
- Choose compounding frequency — daily, monthly, quarterly, or annually.
- Click Calculate — see maturity value, interest earned, effective APY, and the yearly schedule.
The CD Formulas
Effective APY: (1 + APR÷n)n − 1 | n = compounding periods per year
Worked example
$10,000 at 5% APR for 5 years, compounded monthly:
- Maturity: $10,000 × (1 + 0.05÷12)60 = $12,833.59
- Interest: $12,833.59 − $10,000 = $2,833.59
- True APY: (1 + 0.05÷12)12 − 1 = 5.116% — higher than the 5% APR
APR vs. APY: Why It Matters
| 5% APR compounded… | Effective APY | $10k over 5 yrs |
|---|---|---|
| Annually | 5.000% | $12,762.82 |
| Quarterly | 5.095% | $12,820.37 |
| Monthly | 5.116% | $12,833.59 |
| Daily | 5.127% | $12,840.03 |
Same APR, different payouts — always compare the APY column when shopping for CDs.
A CD Ladder, Priced Out
The ladder strategy gets quoted a lot and demonstrated rarely, so here is one with real numbers. Put $25,000 into five $5,000 CDs at 5% APR compounded monthly (5.116% APY), one maturing each year:
| Rung | Term | Value at maturity | Interest earned |
|---|---|---|---|
| 1 | 1 year | $5,255.81 | $255.81 |
| 2 | 2 years | $5,524.71 | $524.71 |
| 3 | 3 years | $5,807.36 | $807.36 |
| 4 | 4 years | $6,104.48 | $1,104.48 |
| 5 | 5 years | $6,416.79 | $1,416.79 |
Held untouched, the rungs pay $4,109.15 of interest in total. The ladder’s magic is what happens at each maturity: rung 1 frees up $5,255.81 after one year. Roll it into a new 5-year CD (the longest, usually best-paying term), and from year five onward a full 5-year CD matures every single year — top-term rates with annual liquidity. If rates have risen, you capture them at each roll; if they have fallen, four-fifths of your money still sits in older, better rates. Real ladders price each rung at that term’s actual rate, so run each rung through the calculator with its own APR before you commit.
The Tax Bill Arrives Every Year, Not at Maturity
One surprise multi-year CDs spring on first-time buyers: in the US the interest is taxable in the year it is credited, even on a 5-year CD you cannot touch. (Multi-year CDs follow the IRS original-issue-discount rules, so the tax follows the accrual, not the payout.) It is ordinary income, taxed at your marginal rate. On our worked example’s $2,833.59 of interest, a saver in the 22% federal bracket keeps $2,833.59 × 0.78 ≈ $2,210.20 after federal tax — a true after-tax APY of roughly 3.99% rather than 5.116%. Two practical consequences: keep a little cash outside the CD for the annual tax bill, and compare CDs against Treasury bills on an after-tax basis — T-bills skip state and local tax entirely, which can let a lower headline rate win for savers in high-tax states.
Breaking a CD early: the real price
Early-withdrawal penalties are usually quoted in months of interest — six months is common. On $10,000 at 5% that is roughly $250. Two things follow: the penalty only costs you profit you have already earned (early on, if you have earned less than the penalty, it can dip into principal); and breaking an old, low-rate CD to re-buy at a much higher rate can genuinely pay off when the term left is long — but only if the extra interest over the remaining term clearly beats the penalty. Run both numbers in the calculator before deciding, because the penalty is certain and the rate gain depends on rates staying put.
Who This Calculator Is For
- Savers comparing CD offers across banks and terms.
- Emergency-fund builders deciding between a CD ladder and a high-yield savings account.
- Near-retirees parking cash safely while keeping it growing.
- Anyone offered a “special rate” — verify the APY before you lock up money.
CD tips
- Build a ladder: split money across 1-, 2-, 3-, 4-, 5-year CDs; as each matures, roll into a new 5-year — liquidity plus top rates.
- Watch the early-withdrawal penalty: typically 3–6 months of interest; never lock up money you might need.
- No-penalty CDs exist for flexibility, usually at slightly lower rates.
- Check FDIC insurance: most bank CDs are insured up to the legal limit per depositor, per bank.
Frequently Asked Questions
What is a CD (certificate of deposit)?
A CD is a bank deposit that locks your money for a fixed term (months to years) in exchange for a guaranteed interest rate, usually higher than a savings account. Withdrawing early triggers a penalty, typically several months of interest.
What is the difference between APR and APY?
APR is the stated annual rate before compounding; APY is the true yearly return after compounding. A 5% APR compounded monthly is a 5.116% APY. Always compare CDs by APY.
How is CD interest calculated?
A = P(1 + APR/n)nt, where n is compounding frequency and t is years. Banks compound daily, monthly, quarterly, or annually — more frequent compounding means slightly more interest.
What happens when a CD matures?
You typically get a grace period (often ~10 days) to withdraw or move the money. Do nothing and most banks auto-renew into a new CD at current rates — which may be worse than what’s available elsewhere. Calendar your maturity dates.
Are CDs safe?
CDs from FDIC-insured banks (or NCUA-insured credit unions) are among the safest investments: principal plus earned interest is insured up to legal limits. The main risks are inflation eroding purchasing power and opportunity cost.
What is a CD ladder?
Splitting a lump sum across multiple CDs with staggered maturities (e.g., 1–5 years). As each rung matures you get regular access to cash while capturing longer-term rates. It’s the classic answer to “I want yield but might need the money.”
What is the difference between a bank CD and a brokered CD?
A bank CD is bought directly from the issuing bank and is locked until maturity or an early-withdrawal penalty. A brokered CD is bought through a brokerage account, is still FDIC-insured up to legal limits, often pays slightly higher rates — and can be sold to another investor on the secondary market instead of surrendered, so you avoid the bank’s early-withdrawal penalty but may receive less (or more) than face value depending on rates. This calculator’s maths — deposit, rate, compounding, term — applies to both.
CD or high-yield savings account — which is better?
It is a trade between certainty and flexibility. A CD guarantees its rate for the full term and usually pays a bit more; a high-yield savings account lets you withdraw anytime but its rate floats and can be cut without notice. Money with a known future due date (a house deposit, next year’s tuition) suits a CD; a true emergency fund suits the savings account; money that is partly both is exactly what a CD ladder is for.
Final Thoughts
CDs reward patience with certainty — but only if you compare the right numbers. Run any offer through the calculator above, compare APYs (never APRs), and ladder your terms so opportunity never knocks while your money is locked up.
Growing Savings?
Compare long-term growth with our CAGR calculator and check home budgets with our home affordability calculator.