CD Tool
Explore certificate of deposit returns using flexible terms, annual rates, compounding schedules and interest payouts. Include tax, inflation, opening fees and early withdrawal penalties, then review projected balances, annualised yield, interest schedules and exportable results.
Tax is estimated as interest accrues. Early withdrawal penalty is based on simple interest at the stated annual rate, capped at interest earned. No recurring contributions are assumed for a fixed-term CD.
| Period | End date | Interest | Tax | Payout | Balance |
|---|
Illustrative estimates only; bank rounding, withdrawal rules and tax treatment can differ.
Table of Contents
Highlights
- Compare APR and APY with six compounding intervals or simple interest.
- Model reinvested interest or regular interest payouts.
- Factor in estimated tax, inflation, opening fees and early withdrawal penalties.
- Explore interactive balance charts and monthly or yearly interest schedules.
- Export cash flows as CSV, full results as JSON or charts as SVG.
How CD Tool Works?
A certificate of deposit (CD) pays interest on an initial deposit over a fixed term. Enter the deposit, quoted annual rate, start date and term in days, months or years. Select APR or APY, daily, weekly, monthly, quarterly, semi-annual or annual compounding, or simple interest. Interest accrues each day on the applicable balance under the selected Actual/365 or Actual/360 day-count basis and is credited at each compounding date or on closure.
For a positive compounding frequency, an APY quote is converted to an equivalent nominal annual rate before daily accrual:
Here, m is compounding events per year and r is the nominal annual rate expressed as a decimal. With APR, the quoted percentage is used directly as the nominal rate; simple interest uses the quoted annual rate without reinvestment.
Each day's interest is calculated as follows:
B is the current deposit balance for compounding interest, or the original principal for simple interest; D is 365 or 360. At each credit date, estimated tax is deducted from accrued interest. The remainder is either reinvested or paid out. Under simple interest, net interest is paid out rather than added to principal.
| Output | Calculation |
|---|---|
| Total interest earned | Sum of all gross interest credited |
| Final deposit balance | Principal plus reinvested after-tax interest, less any early withdrawal penalty |
| After-tax profit | Final deposit balance + net interest paid out − initial deposit − opening fee |
| Annualised yield | Annualised ratio of total realised value to deposit plus opening fee |
| Inflation-adjusted total | Total realised value discounted by the assumed annual inflation rate |
If an early withdrawal month falls before maturity, the projection ends at that date. The estimated penalty is the smaller of gross interest earned and the principal multiplied by the nominal annual rate and the stated penalty months divided by 12. Annualised yield and inflation adjustments use elapsed days divided by 365.2425 years.
The results show the projected deposit balance, interest, net profit, effective annual yield, inflation-adjusted total, interactive balance chart and selectable monthly or yearly interest schedule. CSV, JSON and SVG exports are available.
Practical Use Cases
First-time savers: Compare how a $10,000 deposit might grow over 24 months using a 4.5% quoted APY and monthly compounding, before committing savings to a fixed term.
Retirees seeking income: Choose interest paid out rather than reinvested to estimate cash distributions while keeping the deposit principal separate from interest income.
Rate shoppers: Enter an APR or APY and test different compounding frequencies and deposit terms to understand the projected difference between offers.
Tax-conscious investors: Set an estimated interest tax rate and opening fee to compare gross interest with after-tax profit and the effective annualised return.
Household budget planners: Apply an assumed inflation rate to see the projected purchasing-power value of a CD at the end of the selected term.
Savers anticipating early access: Specify a withdrawal month and a penalty measured in months of interest to estimate the effect of ending a CD before maturity.
Accuracy and Limitations
Projections use daily accrual, the selected 365- or 360-day denominator and specified credit dates; actual banks may use different posting dates, rounding or day-count rules. APY is converted to a nominal rate before daily accrual, so results may differ slightly from advertised yields. Tax is deducted when interest is credited, without individual tax brackets or withholding rules. Opening fees reduce net profit but not the interest-bearing balance. An early-withdrawal penalty is an estimate capped at gross earned interest, not a bank-specific rule. Annualised yield treats interest already paid out as part of final value rather than modelling the timing or reinvestment of those payments. Inflation is assumed constant, and rates, tax and inflation do not change during the term.
