Calculator Methodology

Every calculator on Rupee Rubric runs entirely in your browser. No data you enter is sent to any server. Below are the formulas and assumptions behind each tool.

SIP Calculator

Uses the standard future value of a recurring investment formula with monthly compounding:

FV = P × [(1 + r)ⁿ - 1] / r × (1 + r)

Where P = monthly SIP amount, r = monthly rate (annual rate ÷ 12), n = total months.

The step-up variant increases P by a fixed percentage each year. The inflation-adjusted toggle deflates the result using the same compounding formula at the specified inflation rate.

EMI Calculator

Uses the reducing balance method, which is the standard used by all Indian banks:

EMI = P × r × (1 + r)ⁿ / [(1 + r)ⁿ - 1]

Where P = principal, r = monthly interest rate, n = loan tenure in months.

The extra payment feature recalculates the amortisation schedule month by month, applying extra payments to principal and recalculating remaining interest accordingly.

Tax Calculator

Applies FY 2025–26 income tax slabs for both old and new regimes as per the Finance Act 2025. Standard deduction of ₹75,000 is applied under the new regime; ₹50,000 under the old regime. All deductions (80C, 80D, HRA, NPS 80CCD(1B)) are applied as entered. Health and education cess is calculated at 4% on the total tax. Surcharge is applied at the applicable rate for income above ₹50L.

Inflation Calculator

Uses standard compound inflation formula:

Future Value = Present Value × (1 + inflation rate)ⁿ

The "real value" mode inverts this to show what a future amount is worth in today's money. The "buying power" mode shows how much of today's purchasing power is lost over time.

FD vs SIP Calculator

FD returns are calculated with quarterly compounding (standard for most Indian banks). Interest is taxed at the applicable income slab rate entered. SIP returns use the same monthly compounding formula as the SIP calculator. LTCG on equity funds is taxed at 12.5% (above ₹1.25L threshold, per Finance Act 2024). Dividend Distribution Tax is not applied as most funds offer growth options.

Savings Calculator

Calculates how long to reach a savings goal given a monthly savings amount and an assumed annual return, using the future value formula with monthly compounding.

Limitations

All calculators use fixed assumed rates of return unless you change them. Real-world returns vary. Fund charges (expense ratio, exit loads) reduce actual corpus but are not automatically deducted — enter them into the rate field manually for a more accurate picture. Tax calculations assume Indian resident individual status; NRI taxation differs.

If you find a formula error, contact us with the specific calculator and the discrepancy.