§ Tools / Series 03 · Personal finance
Fixed deposit calculator
A deterministic, stateless calculator that turns a single term deposit into its full output picture: maturity value, gross interest, after-tax maturity, effective annual yield, and side-by-side comparison of how different compounding frequencies change the same deposit. Product-neutral: works as a Fixed Deposit, Term Deposit, or Certificate of Deposit — no country-specific tax law is hardcoded.
§ Transparency layer
Every output has a formula-trace line. Every input is audited as used / defaulted / unused. Nominal vs effective rate is a first-class toggle, not buried. Cumulative vs payout are explicitly separate modes — you cannot accidentally compare apples-to-oranges.
3
Presets
5
Compounding frequencies
2
Interest modes
5×
Rate scenarios
v1
Methodology
§ Start with a preset
Three product-neutral presets · adjust any field after.
Inputs
Everything you change reruns the math instantly. No save, no login.
Maturity value · gross
$11,607.55
Single deposit of $10,000.00 grows over 3 years at 5% quarterly compounding.
Gross interest$1,607.55
Effective annual yield5.095%
Principal
$10,000
10,000 × ones
Periodic rate
1.2500%
per quarterly · 4×/yr
Compounding periods
12
3 years × 4
Total cash received
$11,608
paid at maturity
§ Compounding comparison
How much does compounding frequency actually move the maturity number?
| Compounding | Periods / yr | Periodic rate | Effective annual | Maturity | Interest | vs yearly |
|---|---|---|---|---|---|---|
| Yearly | 1 | 5.0000% | 5.000% | $11,576.25 | $1,576.25 | — |
| Half-yearly | 2 | 2.5000% | 5.062% | $11,596.93 | $1,596.93 | +$20.68 |
| Quarterly selected | 4 | 1.2500% | 5.095% | $11,607.55 | $1,607.55 | +$31.30 |
| Monthly | 12 | 0.4167% | 5.116% | $11,614.72 | $1,614.72 | +$38.47 |
| Daily | 365 | 0.0137% | 5.127% | $11,618.22 | $1,618.22 | +$41.97 |
§ Rate scenarios
What if the bank's quote moves by 25 bps before you lock in?
-50 bps
4.50%
$11,437
interest $1,437
-25 bps
4.75%
$11,522
interest $1,522
Base
5.00%
$11,608
interest $1,608
+25 bps
5.25%
$11,694
interest $1,694
+50 bps
5.50%
$11,781
interest $1,781
§ Yearly schedule
How the balance compounds year-by-year
| Year | Opening balance | Interest credited | Closing balance |
|---|---|---|---|
| Y1 | $10,000.00 | +$509.45 | $10,509.45 |
| Y2 | $10,509.45 | +$535.41 | $11,044.86 |
| Y3 | $11,044.86 | +$562.68 | $11,607.55 |
§ Formula trace
- principal = 10000 × Ones = 10000.00 USD
- periodsPerYear = 4 (quarterly)
- periodicRate = 1.250000% (from 5% nominal apr)
- periods = round(3 × 4) = 12
- effectiveAnnualYield = (1 + periodicRate)^4 − 1 = 5.094534%
- maturityAmountGross = principal × (1 + periodicRate)^periods = 11607.55
- grossInterestEarned = maturity − principal = 1607.55
§ Input audit
amountused
annualRatePctused
compoundingused
currencyused
interestModeused
payoutFreqdefaulted
rateConventionused
taxRatePctdefaulted
tenureYearsused
unitused
withholdingRatePctdefaulted
§ Warnings
- No tax or withholding modeled — FD/CD interest is generally taxable as ordinary income; the after-tax maturity will be lower than shown.
- Early-withdrawal penalties and deposit-insurance caps are not modeled. Country-specific tax (TDS thresholds, slabs, exemptions) is whatever rate you type — no jurisdictional rules are hardcoded.
§ Golden references · locked in tests
Principal $1,000 · 12% · 10 years — the same deposit at four compounding frequencies. The spread is the whole reason the comparison table exists.
Yearly
$3,105.85
Quarterly
$3,262.04
Monthly
$3,300.39
Daily
$3,319.46
§ Related calculators
§ Same engine, headlessly
Rate normalization, compounding comparison, rate scenarios, yearly schedule, formula trace, and input audit are all reachable as a stateless REST endpoint and as MCP tools. Unknown inputs are rejected with a 422; ignored-in-context inputs are flagged in the audit — no input is silently consumed.
POST/api/v1/financial-calculators/fixed-deposit/calculate
POST/api/v1/financial-calculators/fixed-deposit/run
GET/api/v1/financial-calculators/fixed-deposit/schema
GET/api/v1/financial-calculators/fixed-deposit/defaults
MCP tool
calculate_fixed_deposit_returnsmethodology_version = financial-calculators.v1 · canonical = /en/tools/fixed-deposit-calculator
§ What v1 does not include
- No workbook save/load — v1 is intentionally stateless.
- No early-withdrawal penalty modeling.
- No country-specific tax law (TDS thresholds, slab rules, exemptions) — tax is whatever rate you type.
- No leap-year handling in daily compounding (uses 365 days flat; surfaced in warnings).
- No premium prefill — there is no ticker data for FDs.
§ FAQ
Four things worth knowing
Q01Is this a Fixed Deposit, Term Deposit, or Certificate of Deposit calculator?+
It is all three. The math is identical — a single deposit, a fixed rate, a fixed compounding frequency, and a maturity date. The page is intentionally product-neutral: no country-specific tax law, TDS thresholds, deposit-insurance limits, or promotional-rate restrictions are hardcoded. Use it with the terminology of whichever market you are in.
Q02Why does the effective annual yield differ from the rate I typed?+
Banks usually quote the nominal APR (the rate compounded n times per year). A 12% nominal rate compounded daily produces an effective annual yield of about 12.747%. Toggle Rate convention → Effective annual to treat your input as the already-compounded yield instead. The Compounding comparison table makes the gap visible across yearly / half-yearly / quarterly / monthly / daily.
Q03Cumulative vs payout — what is the difference?+
Cumulative reinvests every period of interest until maturity (compound growth). Payout returns the principal at maturity and pays simple interest periodically (a CD-style income stream). The two are not interchangeable — payout deposits do not benefit from compounding, which is why cumulative deposits at the same nominal rate end up with a higher total cash received. We model the two as separate modes precisely so the gap is visible.
Q04How is tax computed?+
Tax and withholding are both applied to the gross interest earned. The tool does not model any country-specific tax law (no TDS thresholds, no slab logic, no exemptions) — it is whatever rate you type. After-tax maturity = principal + gross interest × (1 − tax rate). Withholding is reported separately so you can model a TDS-style withholding without conflating it with your final tax bill.