Investment Math
Compounding, SIP/lumpsum future value, XIRR, real vs nominal returns, and the Rule of 72.
SIP Future Value
Annuity-due (start of period)
FV = M × [(1+i)ⁿ − 1] / i × (1+i)
- M — Monthly contribution (₹)
- i — Periodic rate (annual ÷ 12)
- n — Number of contributions (months)
Rule of 72
Quick approximation for doubling time at fixed compounding.
Doubling years
t ≈ 72 / r%
- r — Annual rate as percentage (%)
Rule of 72 is most accurate between 6%–10%. For higher rates, the exact log formula gives a tighter answer.
XIRR (irregular cash flows)
XNPV equation solved for r
Σ Cᵢ / (1+r)^(dᵢ−d₀)/365 = 0
- Cᵢ — Cash flow at date dᵢ (negative = invest, positive = redeem) (₹)
- r — Annualised IRR being solved for
Related calculator
SIP Future Value
Project the future value of a Systematic Investment Plan with monthly contributions and assumed CAGR.
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