CD Calculator

Most CD calculators show you one number and stop there, the happy one, what your deposit grows to on the maturity date with interest included. Every free tool gets that part right. The number that actually costs people money is the one they leave out: what you give up if you have to break the CD before the term ends, and you get both figures here. Enter your deposit, the APY, and the term, and you get the maturity value and total interest right away. Then enter a penalty and it shows the case nobody plans for, the one where cashing out early leaves you with less than you put in.

Put $10,000 at 5% APY into a 3-year CD and it matures at $11,576.25, with $1,576.25 of that being interest. Everything runs in your browser, recalculates the instant you change a field, and nothing you type is uploaded.

1. Enter your deposit. This is the lump sum going into the CD. Most banks set a minimum, often between $500 and $1,000, and some have none.
2. Type the APY. Leave the rate mode on APY and enter the annual percentage yield straight from the bank's offer, something like 5 or 4.35. APY is the all-in yearly return with compounding already counted, so the maturity figure comes out exact.
3. Only have a stated rate? Switch modes. If your disclosure lists a nominal rate and a compounding schedule, flip the rate mode to "Stated rate + compounding," choose how often it compounds, and the tool converts it to the effective APY for you.
4. Set the term. Enter the length and pick months or years, whatever the bank offers. Odd terms work fine, an 18-month CD just gets a final partial row in the table.
5. Add an early-withdrawal penalty (optional). Banks quote this as a number of months of interest, usually 3 on a short CD and 6 to 12 on a longer one. Put it in, then say how many months into the term you'd pull the money out, and you see what breaking the CD at that point actually leaves you.

Read off the maturity value, total interest, and the APY applied. The table underneath shows the balance climbing year by year, and if you entered a penalty, the amber box lays out the early-exit math.

This is the whole reason the calculator exists, the number most people never look at until they need their money back.

Pull cash out of a CD before it matures and the bank charges an early-withdrawal penalty, almost always quoted as a set number of months of interest. Three months on a one-year CD, six to twelve on a five-year one, forfeited straight off what you earned.

Enter the penalty months and the month you'd break it, and the amber box works out what your balance had really grown to by that point, then takes the penalty off that. Interest stops the day you cash out, so the exit month does as much work in this number as the penalty does. Break it early enough, before you've piled up much interest, and the penalty is bigger than everything you've earned, so it starts eating into your original deposit. Set a heavy penalty and an early exit month and the "value after penalty" drops below your deposit, exactly the outcome a maturity-only calculator hides from you.

The rule is blunt: only lock up money you're confident you won't need for the full term. If there's a real chance you'll have to touch it, the penalty can cancel out the reason you chose a CD, and that cash is better off in a liquid high-yield savings account even at a slightly lower rate. There's also a no-penalty CD, which exits early for free but pays less in return.

CDs get advertised two ways, so the tool takes either one.

The APY, the annual percentage yield, is what you actually earn once compounding is folded in. That's the default mode and the number you want in almost every case. Type the advertised APY and you're done. The stated rate (the nominal rate) is the base rate before compounding, always a little lower than the APY. If your paperwork only gives you that, along with how often the CD compounds, switch to "Stated rate + compounding" and the tool converts it for you. Either way it runs the projection off one effective yield, so the headline number and the growth table never disagree.

A concrete case. A 4.9% stated rate compounded monthly works out to about 5.01% APY, because each month's interest earns a little of its own interest. It's a small gap, but it's real money on a big deposit held for years.

Compare CDs by APY. US banks must disclose it by law, so it's always printed somewhere, and because it already accounts for compounding, a CD with a lower stated rate but daily compounding can beat one with a higher stated rate compounded once a year. Chasing the compounding frequency itself is mostly wasted effort, two CDs at the same APY pay effectively the same.

People fixate on the rate and underrate the term. Watch what the same 5% APY does to $10,000 over time:

• 1 year: $10,500, so $500 in interest.
• 3 years: $11,576.25, so $1,576.25.
• 5 years: $12,762.82, so $2,762.82.

Same rate, and the five-year interest is more than five times the one-year figure, because the interest keeps compounding on itself. The growth table shows this row by row, the interest column climbs a bit each year as the balance it's earning on gets bigger. One caveat though: longer doesn't always pay more. In some rate environments short CDs out-yield long ones, an inverted curve, because banks expect rates to fall and won't lock in a high long-term payout. So check the actual APY at each term instead of assuming longer wins.