Everyday finance, explained

Make money decisions with clearer numbers.

Compare a loan repayment, plan monthly wealth growth, or calculate your early retirement number—all in your browser, without sharing your financial data.

₹ Indian formatting No sign-up Runs locally

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One question at a time

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01

Loan inputs

Estimate a fixed-rate, reducing-balance monthly payment.

₹1,000 to ₹10 crore
Popular:

Estimated monthly EMI

₹0

per month

Principal
₹0
Total interest
₹0
Total repayment
₹0
How it is calculated

EMI = P × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1), using a reducing-balance monthly interest rate.

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Use realistic inputs

Check the actual interest rate, charges, and repayment schedule in the lender’s documents.

Returns are not fixed

SIP results are mathematical illustrations. Market returns can be lower, higher, or negative.

Keep a margin

Leave room in your budget for fees, emergencies, and changes in income or rates.

How Rupee Lab Works: Loan EMI, SIP Wealth & FIRE Planning

Rupee Lab provides transparent, privacy-first financial calculators calibrated for Indian household economics, including reducing-balance loan interest, rupee-cost averaging via mutual fund SIPs, and realistic safe withdrawal rates under Indian inflation conditions.

Step-by-Step: How to Use These Calculators

  1. Select your goal: Switch between the EMI Calculator (for loans and prepayments), SIP Calculator (for systematic wealth accumulation), or FIRE Calculator (for financial independence and early retirement).
  2. Enter your parameters: Specify your principal amount, interest rate or expected return percentage, and duration in years or months. Use the step-up toggle on SIPs to reflect expected yearly salary hikes.
  3. Inspect your repayment & growth breakdown: Review the principal vs. interest breakdown, total payable obligation, or compounding wealth multiplier.
  4. Switch languages anytime: Click the English/తెలుగు toggle at the top right to view terms and labels in Telugu or English.

Practical Financial Scenarios

1. Home Loan Prepayment Optimization

Understand how paying just one additional EMI every year or increasing your monthly EMI by 5% can reduce a 20-year home loan by 4–6 years, saving ₹8,00,000 to ₹15,00,000 in compound interest.

2. Disciplined Step-Up Wealth Creation

Salaries increase over time. By enabling a 10% annual step-up on a ₹10,000 monthly SIP, an investor accumulates more than double the corpus compared to a flat SIP over a 15-year horizon.

3. Inflation-Resilient Indian FIRE

The standard US 4% rule (25x expenses) often fails in India due to 6%–7% retail inflation and 10%+ healthcare inflation. Plan with a conservative 30x–33x corpus (3%–3.33% Safe Withdrawal Rate) to protect longevity.

Mathematical Formulas & Methodology

1. Reducing-Balance Loan EMI Formula:

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

Where P = Principal loan amount, r = Monthly interest rate (Annual rate ÷ 12 ÷ 100), and n = Loan tenure in months.


2. Monthly SIP Compound Interest Formula:

M = P × [((1 + i)^n - 1) / i] × (1 + i)

Where P = Monthly SIP installment, i = Monthly expected rate of return (Annual return ÷ 12), and n = Number of months.


3. Indian FIRE Retirement Target Corpus:

Target Corpus = Annual Household Expenses ÷ Safe Withdrawal Rate (SWR)

At a 3.33% SWR, the required target corpus is exactly 30 × Annual Expenses.

Worked Practical Example

Case: ₹30,00,000 Home Loan at 8.75% for 20 Years (240 Months)

  • Monthly EMI: ₹26,511
  • Principal Repaid: ₹30,00,000
  • Total Interest Paid: ₹33,62,717
  • Total Amount Paid: ₹63,62,717

Key Insight: On a standard 20-year loan at 8.75%, the interest paid exceeds the actual principal borrowed. Making early lump-sum prepayments toward principal drastically slashes this interest component.

Limitations, Accuracy Notes & Privacy Disclosures

Zero Server Storage: Rupee Lab operates 100% within your client browser. Your loan figures, salary details, or investment targets are never transmitted to any external server or stored in cookies.

Tax & Regulatory Note: Calculations do not factor in personal income tax deductions (such as Section 80C principal relief or Section 24(b) home loan interest exemptions up to ₹2 Lakhs) or Long Term Capital Gains (LTCG) tax of 12.5% on equity mutual fund gains exceeding ₹1.25 Lakh per financial year.

Frequently Asked Questions (FAQs)

How does prepaying home loan principal affect total interest?
Prepayments go directly toward reducing the outstanding loan principal. Because Indian home loans use monthly reducing-balance compounding, reducing the principal immediately lowers the interest charged in all subsequent months, shortening your overall tenure and saving substantial money.
What is a realistic CAGR expectation for equity mutual funds in India?
Historically, broad Indian equity benchmark indices (such as Nifty 50 and S&P BSE Sensex) have delivered 11%–13% annualized nominal returns over 10-to-15 year horizons. However, past returns do not guarantee future performance and equity investments carry market risk.
Why is the US 4% FIRE rule considered risky for Indian households?
The 4% rule originated from the US Trinity Study, which modeled a low-inflation economy (2%–3%). In India, consumer price inflation typically runs at 6%–7% and healthcare costs inflate at 10%–14% annually. A 25x corpus (4% withdrawal) carries elevated sequence-of-returns risk; hence Indian planners recommend at least 30x (3.33% SWR) to 33x (3% SWR).
Are my financial numbers or bank details tracked or logged?
No. Rupee Lab does not require an account, mobile number, or login. All calculations are executed directly in your browser's JavaScript engine, ensuring complete confidentiality.

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