How Our Calculators Work
Understanding the methodology behind BudgetGear's car finance calculators
Car Affordability Calculator
The 20/4/10 Rule Methodology
Our car affordability calculator is based on the proven 20/4/10 rule, a financial guideline used by banks and financial advisors worldwide:
20% Down Payment
You should pay at least 20% of the car's on-road price upfront. This reduces your loan burden, gets you better interest rates, and ensures positive equity from day one.
4-Year Maximum Tenure
Limit your car loan to 4 years (48 months) to minimize interest costs and avoid being underwater on your loan as the car depreciates.
10% of Gross Income
Total monthly car expenses (EMI + fuel + insurance + maintenance) should not exceed 10% of your gross monthly income.
Calculation Formula
Maximum Car Price = (Monthly Income × 0.10 - Non-EMI Costs) × Loan Multiplier ÷ 0.80
Where Loan Multiplier is calculated based on the interest rate and 48-month tenure using the standard EMI formula.
EMI Calculator
Standard EMI Formula
We use the industry-standard EMI calculation formula used by all major Indian banks including SBI, HDFC, ICICI, and Axis Bank:
EMI = [P × R × (1+R)^N] / [(1+R)^N - 1]
Where: P = Principal loan amount, R = Monthly interest rate, N = Loan tenure in months
What We Calculate
- Monthly EMI payment
- Total interest payable over loan tenure
- Total amount payable (principal + interest)
- Month-by-month amortization schedule
- Principal vs interest breakdown for each payment
Prepayment Calculator
Prepayment Impact Analysis
Our prepayment calculator shows you exactly how making additional payments affects your loan:
- Interest savings from prepayment
- Reduced loan tenure
- New EMI amount (if you choose to reduce EMI)
- Comparison of different prepayment strategies
- Break-even analysis including prepayment penalties
Note: We factor in prepayment penalties charged by banks (typically 2-5% of prepayment amount) to give you accurate savings calculations.
Data Sources & Accuracy
Our calculators use current market data from reliable sources:
- Interest rates: Updated monthly from official bank websites (SBI, HDFC, ICICI, Axis Bank)
- Insurance costs: Based on IRDAI guidelines and major insurer rates
- Fuel prices: Current retail prices from Indian Oil, Bharat Petroleum, Hindustan Petroleum
- Depreciation rates: Industry standard rates verified by automotive associations
- Maintenance costs: Average costs from authorized service centers
Your Privacy Matters
All calculations are performed locally in your browser. We do not store, transmit, or share any of your financial information. Your data never leaves your device.
Our calculators are 100% free to use with no registration required.