Fixed Deposit Calculator

Principal:

Use the amount on the offer or renewal notice, before interest.

Rate basis:

Match the wording printed on the deposit offer.

Quoted rate:

For example, enter 4.25 for a 4.25% annual quote.

% / year

Whole years:

The combined term must be at least one month.

years

Extra months:

A partial final credit window becomes a stub period when needed.

months

Interest crediting:

Match the contract: monthly, quarterly, semi-annual, or annual.

Interest handling:

Use the setting stated in the account disclosure.

Deposit start date:

Use the opening or renewal date shown by the bank.

Tax on interest:

Use 0 for a pre-tax, tax-free, or tax-deferred comparison.

Tax timing:

This setting is neutral while the tax rate remains 0%.

Annual inflation:

Use 0 when only nominal dollars are needed.

% / year

Coverage limit:

Use 0 to disable this generic exposure check.

Metric	Value	Decision note	Copy
{{ row.label }}	{{ row.value }}	{{ row.note }}

Period	Credit window	Days	Opening	Gross	Tax	Paid out	Ending	Copy
{{ row.period_number }}	{{ row.start_date }} – {{ row.end_date }}	{{ row.days }}	{{ money(row.opening_balance) }}	{{ money(row.gross_interest) }}	{{ money(row.tax_paid) }}	{{ money(row.payout_cash) }}	{{ money(row.ending_balance) }}

Year	Gross interest	Tax	Paid out	Ending balance	Total value	Copy
{{ row.year }}	{{ money(row.gross_interest) }}	{{ money(row.tax_paid) }}	{{ money(row.payout_cash) }}	{{ money(row.ending_balance) }}	{{ money(row.total_value) }}

A fixed deposit exchanges access to cash for a stated return over a defined term. The opening principal, quoted rate, calendar dates, interest-credit schedule, and treatment of each credit together determine what is on deposit at maturity and what may have been paid out along the way.

The rate label matters before any arithmetic begins. Annual percentage rate (APR) is treated here as a nominal annual rate allocated by actual days. Annual percentage yield (APY) is treated as a one-year growth factor that already reflects compounding. Entering an APY as APR can overstate or understate the result, depending on the credit frequency.

Fixed deposit choices that change the maturity projection
Contract term	What it changes	What to verify
APR or APY	How the annual quote becomes a credit-period rate	The exact wording on the offer
Crediting frequency	When interest is posted and can start earning more interest	Monthly, quarterly, semi-annual, or annual
Reinvest or pay out	Whether net interest stays in the deposit balance	The account's interest-disposal instruction
Term and start date	The maturity date and actual days in every credit window	The opening or renewal notice

Reinvested interest compounds because each net credit increases the balance used by the next period. Paid-out interest becomes separate cash and leaves the on-deposit balance unchanged. Both paths can have the same gross credit for the first period and diverge afterward.

Calendar timing introduces small differences that a simple “months divided by twelve” estimate misses. A monthly window may contain 28, 29, 30, or 31 days, and a term ending between normal credit dates creates a stub period. The start date therefore affects the maturity value even when principal, rate, and term length in months stay the same.

Tax, inflation, and deposit coverage are separate planning assumptions. A tax percentage models a simple deduction from interest, not a jurisdiction's filing rules. Inflation discounts the projected cash value using one constant annual rate; it does not forecast prices. A coverage limit compares a user-entered amount with the highest modeled on-deposit balance and cannot determine legal insurance eligibility, ownership categories, or aggregation across accounts.

Bank disclosures can include early-withdrawal penalties, tiered or stepped rates, minimum balances, nonstandard day-count conventions, promotional bonuses, renewal terms, and different rounding rules. Those contract terms take priority over an estimate. The result is educational planning information, not financial, tax, or legal advice.

How to Use This Tool:

Copy the contract terms directly from the deposit offer or renewal notice before adding planning assumptions.

Enter the Principal, choose Rate basis, and enter the Quoted rate exactly as disclosed.
Set Whole years, Extra months, Interest crediting, Interest handling, and Deposit start date. The combined term must be at least one month.
Use the advanced assumptions only when needed. Enter Tax on interest, Tax timing, Annual inflation, or a jurisdiction-appropriate Coverage limit; zero leaves each comparison neutral or off.
Read FD Readiness first, then inspect Credit Schedule for day counts and posted credits. Compare total value, real value, yields, and peak balance with the bank's disclosure.

Interpreting Results:

Total value combines the maturity settlement with any net interest paid out during the term. Maturity settlement is the cash released at maturity itself. For a payout deposit, these are different figures.

Gross interest is before modeled tax; Net interest is total value minus opening principal.
Real value expresses the modeled outcome after discounting by the entered constant inflation rate. It is a scenario, not a forecast.
After-tax annual yield and real annual yield annualize the modeled start-to-end change, so they can be compared across different terms.
A positive Coverage gap means peak on-deposit balance exceeded the limit you entered. Verify actual coverage with the relevant insurer or regulator.

Technical Details:

The projection advances through calendar credit windows from the start date. Each period uses its actual number of days, calculates gross interest on the opening on-deposit balance, rounds money to cents, applies modeled tax when selected, and either reinvests or pays out the net credit.

Formula Core:

APR and APY quotes use different period-rate equations. The APY path preserves the annual growth factor across a fractional year; the APR path prorates the nominal annual rate by days.

\begin{aligned} r_{period,APR} & = \frac{r}{100} \frac{d}{365} \\ r_{period,APY} & = {(1 + \frac{r}{100})}^{\frac{d}{365}} - 1 \\ I_{gross} & = roundCent (B r_{period}) \\ I_{net} & = I_{gross} - roundCent (I_{gross} t) \end{aligned}

r is the quoted annual percentage, d is days in the credit window, B is opening balance, and t is the tax rate written as a decimal. The tax subtraction in the final line applies when tax is deducted at each credit; maturity-tax mode reserves the modeled tax until the end instead.

Equivalent rate figures translate the quote using the selected number of credit periods per year.

\begin{aligned} APY & = 100 [{(1 + \frac{APR / 100}{n})}^{n} - 1] \\ APR & = 100 n [{(1 + APY / 100)}^{\frac{1}{n}} - 1] \end{aligned}

n is 12 for monthly crediting, 4 for quarterly, 2 for semi-annual, and 1 for annual.

Inflation and annualized outcome rates use the total modeled day count D.

\begin{aligned} RealValue & = \frac{TotalValue}{{(1 + i)}^{\frac{D}{365}}} \\ AnnualYield & = 100 [{(\frac{EndValue}{Principal})}^{\frac{365}{D}} - 1] \end{aligned}

i is the entered annual inflation rate as a decimal. After-tax yield uses total value as the ending value; real yield uses real value.

Mechanism Core:

Fixed deposit period calculation sequence
Stage	Reinvested interest	Paid-out interest
Gross credit	Opening balance × period rate, rounded to cents
Tax at each credit	Gross credit × tax rate, rounded to cents and deducted immediately
Net credit	Added to on-deposit balance	Added to payout cash; deposit balance stays unchanged
Tax at maturity	Modeled tax on accumulated gross interest is reserved and deducted at maturity
Final value	Maturity balance after reserved tax	Returned principal plus payout cash minus reserved tax

The maturity date is found by adding whole calendar months and clamping the day when the destination month is shorter. A partial final credit window becomes one stub period. The coverage comparison uses the highest on-deposit balance, not total value after paid-out cash is added.

Limitations and Privacy Notes:

The model does not cover early-withdrawal penalties, tiered or stepped rates, bonuses, fees, automatic renewal, or bank-specific interest conventions.
Tax is a flat scenario percentage. It does not model brackets, withholding rules, exemptions, filing dates, or jurisdiction-specific treatment.
The coverage limit is supplied by the reader. Eligibility can depend on institution, ownership category, account aggregation, accrued interest, and current law.
The inputs and calculations stay in the browser; no account number or identity information is required.

Worked Example:

A six-month APY quote with a stub credit

A $1,000 deposit opened on January 1, 2026 for six months at 6.18% APY has 181 modeled days to July 1. With annual crediting and reinvestment, the six-month term becomes one stub credit. The APY period equation produces $30.18 of gross interest after cent rounding, for a total value of $1,030.18 before tax and inflation assumptions. Annualizing that calendar result gives about 6.1794%, close to the quote but not numerically identical because the credited dollars were rounded to cents.

References:

Appendix A to Part 1030 — Annual Percentage Yield Calculation, Consumer Financial Protection Bureau.
Definitions for Regulation DD, Consumer Financial Protection Bureau.
Deposit Insurance FAQs, Federal Deposit Insurance Corporation, updated April 1, 2024.