Calculation Methodology
This page documents the formulas behind every FinMatz calculator. Each formula is version-controlled and validated against test vectors (expected outputs for known inputs). All calculations run client-side in your browser.
Core Formulas
| Tool | Formula (concept) |
|---|---|
| SIP | FV = P × [((1+i)n − 1) / i] × (1+i) |
| Step-Up SIP | Sum of annual SIP tranches with periodic increase, compounded monthly |
| Lumpsum | FV = P × (1+r)n |
| CAGR | CAGR = (End/Begin)1/years − 1 |
| SWP | Iterative monthly: balance grows by return, reduced by withdrawal |
| EMI / Home / Personal / Car Loan | EMI = P×r×(1+r)n / ((1+r)n − 1) |
| Income Tax | Slab-based, selectable regime, deductions, cess |
| GST | GST = amount × rate% (inclusive/exclusive modes) |
| Salary | CTC → gross → deductions (PF, tax) → net take-home |
| Gratuity | (15/26) × last drawn salary × years of service |
| PF | Employee + employer contributions compounded at notified rate |
| Retirement | Required corpus from target income, horizon, inflation |
| Inflation | Future value = amount × (1+inflation)years |
Assumptions & Updates
Rate and slab assumptions (tax, PF, gratuity) are reviewed and updated when rules change. Each tool shows its assumptions inline. Results are estimates and not financial advice — see our disclaimer.