FD Formula

Finance Formula • Published on September 01, 2026 • Last updated September 01, 2026

Mathematical Equation

$$A = P \times \left(1 + \frac{r}{n}\right)^{nt}$$

Variable Definitions

Final maturity amount (principal + interest)

Principal deposit amount invested

Annual nominal interest rate (as a decimal)

Compounding frequency per year (standard bank FDs compound quarterly, so n = 4)

Deposit tenure in years

Detailed Explanation

In-Depth Guide

Key Concept

A Fixed Deposit (FD) is a secure investment offered by banks and financial institutions where you deposit a lump sum for a fixed tenure at a guaranteed interest rate.

FDs usually calculate compound interest on a quarterly basis.

It offers steady, predictable growth on capital.

How to Calculate: Step-by-Step

1. Identify the principal deposit ($P$). 2. Identify the bank's annual interest rate ($R$) and convert to decimal ($r = R / 100$). 3. Identify the compounding frequency ($n = 4$ for quarterly, which is standard). 4. Identify the tenure in years ($t$). 5. Calculate the maturity amount ($A$) using the formula: $A = P \times (1 + r/n)^{n \times t}$. 6. Subtract the principal ($P$) from ($A$) to find the total interest earned.

Worked Calculation Example

You invest $20,000 in a fixed deposit for 3 years at an annual interest rate of 7%, compounded quarterly: - Principal ($P$) = $20,000 - Annual nominal rate ($r$) = 7% = 0.07 - Compounding frequency ($n$) = 4 (quarterly compounding) - Tenure ($t$) = 3 years - Calculate using the formula: $$A = 20,000 \times \left(1 + \frac{0.07}{4}\right)^{4 \times 3} = 20,000 \times (1.0175)^{12}$$ $$(1.0175)^{12} \approx 1.2314$$ $$A \approx 20,000 \times 1.2314 = \$24,628.78$$ - Total Interest Earned = $24,628.78 - $20,000 = $4,628.78

Common Use Cases

Calculating low-risk bank deposit maturity values
Comparing different bank interest rates and tenures
Retirement asset planning using steady-yielding vehicles

Frequently Asked Questions

Yes, premature withdrawals are usually allowed, but banks apply a penalty (typically 0.5% to 1%) reducing the effective interest rate earned.

Yes, the interest income is fully taxable under "Income from Other Sources" based on the investor's tax slab. Tax Deducted at Source (TDS) is deducted if interest exceeds specified thresholds.

FD Laddering is a strategy where you split your total investment corpus into multiple FDs with different maturity periods (e.g., 1-year, 2-year, 3-year). As each FD matures, you reinvest it, ensuring liquidity and optimizing interest rate cycles.

Guides

Related guides

Plain-language explainers that sit next to this tool.

Hardware & Device Tests

Are Your Headphones Wired Backwards? Testing L/R Channel Reversal

Learn how headphone left/right channel reversal happens, why casual listening often misses it, and how a simple left-only then right-only test tone sequence makes it obvious.

Sep 29, 2026 5 min

Finance

5 Tools College Students Use to Manage Money and Time

A simple toolkit for students balancing a tight budget, shared living costs, and academic deadlines.

Sep 29, 2026 8 min

Decision Tools

How to Use a Spin Wheel for Fair Random Decisions

A spin wheel is one of the simplest ways to make an unbiased choice between multiple options. Learn how spin wheels ensure fairness and when to use one over a coin flip.

Sep 29, 2026 4 min

Date & Time

How to Calculate Your Exact Age in Years, Months, and Days

Why "current year minus birth year" gives the wrong age, the correct calendar-aware algorithm, and how leap years and February 29th birthdays are handled.