Methodology

Trust is the whole point of CalcNSave, so we're transparent about exactly how our calculators work and where our data comes from. Every calculator also shows its core formula in a "How it's calculated" section on its own page.

How the calculators work

Each calculator is built on a pure, independently tested formula. Our calculation code is covered by an automated test suite that checks results against hand-verified reference values before anything ships.

Fixed Deposit (FD)

Cumulative FDs use compound interest, M = P × (1 + i/n)^(n·t), where n is the number of compounding periods per year. Indian banks most commonly compound quarterly, which is our default; we also let you choose monthly, half-yearly or yearly. The "simple interest" option uses M = P × (1 + i·t) for non-cumulative payout deposits.

Recurring Deposit (RD)

We model an RD as the future value of a monthly-compounding ordinary annuity, M = P × [(1 + i)^n − 1] / i. Note that RD compounding conventions vary between banks (many compound quarterly per RBI norms); we use monthly compounding for transparency and consistency with our SIP calculator, so your bank's figure may differ slightly.

SIP and Lumpsum

SIP uses the future value of an annuity-due (contributions at the start of each month), the industry-standard convention. Lumpsum uses annual compounding. In both cases the "expected return" is an assumption you enter — it is not a guaranteed or predicted return.

EMI

EMI uses the standard formula EMI = P × r × (1 + r)^n / ((1 + r)^n − 1). The maths is identical for home, personal and car loans; only the typical rates and tenures differ.

Income Tax

The tax calculator compares the old and new regimes for the current financial year, applying the standard deduction, slab rates, the Section 87A rebate (with marginal relief), surcharge (with marginal relief) and the 4% Health & Education Cess. Tax law is complex and changes with each Budget; we treat these figures as requiring verification against the Income Tax Department before you rely on them, and the calculator is for estimation only.

Loan Prepayment

We derive your current EMI from the outstanding balance, rate and remaining tenure, then compute your savings by amortising the loan month-by-month. For the "reduce tenure" option we keep the EMI fixed and find the new, shorter tenure; for "reduce EMI" we keep the tenure and compute a lower EMI. Interest saved is the baseline interest minus the new interest.

How we source and verify bank rates

Rate-comparison tables are updated manually, on a monthly basis. We do not scrape bank websites. Every rate we publish carries the date it was last verified, shown as "Rates updated as of …" on the page.

We never publish a rate we haven't verified against a primary source. If we don't yet have verified data for a product, the table shows a "coming soon" note rather than a placeholder number. Rates change frequently, so always confirm the current rate directly with the bank.

Our content standards

• Articles are written and reviewed by a real, named author — see our About page.
• We cite primary sources (RBI, SEBI, the Income Tax Department, official bank pages) for rules and figures.
• We never fabricate a rate, statistic or quote. Where a figure isn't yet verified, we say so.
• Publish dates are honest — we do not backdate content.

Correction policy

If you find an error in a calculation, a rate or an article, please contact us. We investigate promptly and correct verified issues, updating the "last updated" date on materially revised pages.

This page explains our approach but does not constitute financial advice — see our disclaimer.