§ Tools / Series 03 · Personal finance
SIP calculator
A deterministic recurring-investment projection: the systematic investment plan question for India, the monthly investment or DCA question everywhere else. For a contribution, an assumed return, and a tenure it returns the estimated corpus, and, unlike most free tools, it tells you exactly which compounding convention produced the number.
§ Market-linked, not a fixed-rate product
This projects periodic investing under an assumed return. Equity returns are not guaranteed and the smooth curve is not a forecast. For a fixed-rate bank product use the recurring deposit calculator; for one-time investing, the lump-sum calculator.
2
Rate conventions
3
Scenarios
5×5
Sensitivity grid
Goal-seek
Solve for contribution
v1
Methodology
§ Start with a preset
Three product-neutral starting points, adjust anything after.
Inputs
Independent units for the contribution and the lump sum · everything recomputes instantly.
Estimated corpus
$187,187.81
$500 monthly for 15 years at 9%. You invested $90,000.00.
Total earnings$97,188
Growth multiple2.08×
Real corpus · today's money$120,149
Total invested
$90,000
180 contributions
Total earnings
$97,188
51.9% of corpus
Absolute return
108.0%
earnings / invested
Average contribution
$500
flat
Fee drag · lifetime
−$3,434
0.2% annual expense
Periodic rate
0.7333%
per monthly · nominal
§ Invested vs earnings
How much of the corpus is your money vs market growth?
Y0Y2Y4Y6Y8Y10Y12Y14Y15
Total invested Estimated earnings
§ Scenarios
Bear, base, bull, 5% either side of 9%
Bear4.0%
$121,437
Base9.0%
$187,188
Bull14.0%
$300,449
§ Sensitivity
Return × tenure, the corpus across nearby assumptions
| Return ＼ Years | 7y | 11y | 15y | 19y | 23y |
|---|---|---|---|---|---|
| 6.0% | $51,905 | $92,492 | $143,648 | $208,125 | $289,394 |
| 7.5% | $54,939 | $101,447 | $163,670 | $246,921 | $358,303 |
| 9.0%base | $58,198 | $111,497 | $187,188 | $294,674 | $447,314 |
| 10.5% | $61,700 | $122,792 | $214,867 | $353,642 | $562,802 |
| 12.0% | $65,466 | $135,497 | $247,511 | $426,678 | $713,257 |
§ Goal-seek · solve the inverse
How much should you invest each month to hit a target corpus?
$
Required monthly contribution
$750
≈ 750 ones · reaches $280,782
§ Year-by-year schedule
The path, not just the endpoint
| Year | Opening | Contributions | Growth | Fee drag | Closing | Real closing |
|---|---|---|---|---|---|---|
| Y1 | $0.00 | +$6,000.00 | +$293.83 | −$6.86 | $6,293.83 | $6,111 |
| Y2 | $6,293.83 | +$6,000.00 | +$870.58 | −$21.16 | $13,164.42 | $12,409 |
| Y3 | $13,164.42 | +$6,000.00 | +$1,500.19 | −$38.05 | $20,664.61 | $18,911 |
| Y4 | $20,664.61 | +$6,000.00 | +$2,187.49 | −$57.89 | $28,852.09 | $25,635 |
| Y5 | $28,852.09 | +$6,000.00 | +$2,937.77 | −$81.08 | $37,789.86 | $32,598 |
| Y6 | $37,789.86 | +$6,000.00 | +$3,756.80 | −$108.08 | $47,546.66 | $39,820 |
| Y7 | $47,546.66 | +$6,000.00 | +$4,650.89 | −$139.38 | $58,197.56 | $47,320 |
| Y8 | $58,197.56 | +$6,000.00 | +$5,626.91 | −$175.56 | $69,824.47 | $55,120 |
| Y9 | $69,824.47 | +$6,000.00 | +$6,692.38 | −$217.26 | $82,516.85 | $63,242 |
| Y10 | $82,516.85 | +$6,000.00 | +$7,855.47 | −$265.17 | $96,372.32 | $71,710 |
| Y11 | $96,372.32 | +$6,000.00 | +$9,125.16 | −$320.10 | $111,497.48 | $80,548 |
| Y12 | $111,497.48 | +$6,000.00 | +$10,511.19 | −$382.94 | $128,008.66 | $89,783 |
| Y13 | $128,008.66 | +$6,000.00 | +$12,024.23 | −$454.68 | $146,032.90 | $99,441 |
| Y14 | $146,032.90 | +$6,000.00 | +$13,675.93 | −$536.44 | $165,708.83 | $109,553 |
| Y15 | $165,708.83 | +$6,000.00 | +$15,478.98 | −$629.44 | $187,187.81 | $120,149 |
Historical backtest Enterprise
Swap the smooth projection for what actually would have happened running this schedule into a real ticker: money-weighted return (XIRR), max drawdown, and the worst rolling-12-month experience.
§ Formula trace
- contribution = 500 × ones = 500.00 USD / monthly
- periodicRate = R_net / 12 = 0.733333% (R_net after 0.2% fee)
- periods N = 15 × 12 = 180 · timing = beginning-of-period
- futureValue = 187187.81 (initial leg 0.00 + contribution leg 187187.81)
- totalInvested = 90000.00 · totalEarnings = 97187.81
- realFutureValue = FV / (1 + 3%)^15 = 120148.73
- feeDrag = FV(no fee) − FV = 3434.10 over 15y
§ Input audit
contributionused
contributionUnitused
currencyused
expectedReturnPctused
feePctused
frequencyused
inflationPctused
initialAmountdefaulted
initialUnitdefaulted
rateConventionused
returnVariancePctused
stepUpPctdefaulted
taxPctdefaulted
tenureYearsused
timingused
§ Warnings
- Equity returns are not guaranteed. The smooth projection is not a forecast; historical data is not a forecast either.
§ Golden references · locked in tests
Reference case: ₹1,000/month, 12%, 10 years, monthly. Four numbers pinned so the convention can't silently change.
Nominal · end
₹2,30,038.69
Nominal · beginning
₹2,32,339.08
Effective · end
₹2,21,930.04
Effective · beginning
₹2,24,035.89
The ~3.6% gap between nominal-end (₹2,30,038.69) and effective-end (₹2,21,930.04) on the same “12%” input is the whole point: it is which compounding convention you chose, nothing else.
§ Specialized siblings
§ Same engine, headlessly
The deterministic projection, sensitivity matrix, and goal-seek are reachable as stateless REST endpoints and MCP tools. Premium ticker prefill and the historical backtest sit behind scoped API keys. Workbook CRUD is authenticated under calculator_id=sip_investment.
POST/api/v1/financial-calculators/sip/run
POST/api/v1/financial-calculators/sip/sensitivity
POST/api/v1/financial-calculators/sip/solve-contribution
GET/api/v1/stocks/{ticker}/financial-calculators/sip/defaults · enterprise
POST/api/v1/stocks/{ticker}/financial-calculators/sip/backtest · enterprise
MCP tools
calculate_sip_investment · solve_sip_monthly_contribution · backtest_sip_tickermethodology_version = financial-calculators.v1 · canonical = /en/tools/sip-calculator
§ FAQ
Four things worth knowing
Q01Why does “12%” give two different corpus numbers here?+
Because there are two ways to read a 12% return. Nominal APR (the SIP textbook convention) divides it by 12 to get a 1.0000% monthly rate. Effective annual treats 12% as the already-compounded yield, so the monthly rate is (1.12)^(1/12)−1 = 0.948879%. On a ₹1,000/month, 10-year, end-of-period SIP that is ₹2,30,038.69 vs ₹2,21,930.04, a ~3.6% gap on the same input. Most free calculators silently pick one and never tell you. This one makes it a toggle, and defaults to nominal APR for SIP parity.
Q02Beginning or end of period: does the toggle matter?+
Yes. Beginning-of-period (annuity due) means every contribution earns one extra period of growth, which is how most real SIPs behave. End-of-period means the last contribution earns nothing. On a 10-year monthly SIP the gap is about 1% of the final corpus, small per month, real over a decade. The default is beginning-of-period.
Q03How is the step-up SIP computed?+
With an iterative schedule, not a closed-form shortcut. Each year the contribution is multiplied by (1 + step-up rate), then the per-period growth is applied. That same iterative path is what powers missed contributions, non-monthly frequencies, and the historical backtest, so the step-up number is consistent with everything else rather than bolted on.
Q04After inflation, fees, and tax, what is actually left?+
Those are three separate first-class outputs, not blanket disclaimers. Real future value deflates the corpus by inflation into today’s money. After-fee value nets an annual expense ratio out of the return. After-tax value applies an exit tax to positive gains only. You can mix and match them; each appears in the headline and the formula trace.