Frequently Asked Questions

Simple interest is interest calculated only on the original principal. Formula: SI = (P × R × T) / 100. Example: ₹10,000 at 8% per year earns ₹800 every year, no matter what.

Compound interest is interest calculated on the principal plus all interest already credited. Each credited amount starts earning interest itself, so growth accelerates: A = P(1 + r/n)^nt.

Simple interest grows in a straight line — the same amount is added every period. Compound interest grows in a curve — periods add progressively more. With identical inputs and a positive rate, compound interest is always ≥ simple interest at any point in time, with the gap widening the longer you invest.

SI = (P × R × T) / 100, where P is the principal, R the annual rate in percent, and T the time in years. For months, use T = months ÷ 12. Total amount = P + SI.

Use A = P(1 + r/n)^nt, where r is the annual rate as a decimal (8% → 0.08), n the number of compounding periods per year, and t the time in years. Compound interest = A − P. Or simply use the calculator above — it applies the formula for you.

For positive rates and identical inputs, compound interest is always equal to or greater than simple interest. The difference is tiny over very short periods and grows over time. At exactly 0% interest, both methods return the principal unchanged.

With the same nominal annual rate, more frequent crediting (monthly vs annual) produces a higher final amount, because each credited interest starts earning sooner. The example calculator in the Compounding Frequency Explorer shows the size of the effect.

Yes. In the calculator, enter any number of years and months separately. Months are converted to fractional years (6 months = 0.5 years) and both formulas handle the fraction correctly.

Yes — completely free, with no account, no ads-for-data and no limits. All calculations run locally in your browser.

Yes. The site is fully responsive and works on phones from 320px wide, tablets and desktops. Inputs, sliders, charts and results all adapt to the screen size.

Yes. The results dashboard offers Copy results, Download CSV, Print and Share (a URL that encodes only the calculator inputs).

No. The calculators model the raw math of each interest method. Taxes (like TDS on FD interest), fees, rate changes and inflation are not included — real returns will differ. Treat results as pre-tax, fee-free estimates.

The formulas are the standard textbook models (SI = P·R·T/100 and A = P(1 + r/n)^nt, plus continuous compounding A = Pe^rt). The math is exact within floating-point precision and is covered by automated tests. However, results depend entirely on the assumptions you choose, and real products may credit interest differently.

With 0% interest there is nothing to earn: both simple and compound calculations return exactly your principal. The goal calculator will tell you that a target above the principal can never be reached at 0%.

Yes — enter any combination of years and months, and enable Advanced options to add days. Days use an act/365 day-count convention: years + months/12 + days/365.