A home loan, also called a mortgage, is money borrowed from a bank or lender to buy a house. You repay it in monthly installments over a fixed period, usually 10 to 30 years. Understanding how your loan is calculated helps you make smarter decisions, compare lenders, and avoid paying more than you need to.
How is Home Loan Interest Calculated?
Most home loans use a method called amortization. Your monthly payment stays the same every month, but the split between principal and interest changes over time. In early years, most of your payment goes toward interest. As time passes, more goes toward the principal.
The formula used is: M = P × r(1+r)^n / (1+r)^n - 1
- M = Monthly payment
- P = Loan amount (principal)
- r = Monthly interest rate (annual rate ÷ 12)
- n = Total number of payments (years × 12)
Step by Step Example
You borrow $200,000 at 6% annual interest for 20 years:
- Monthly rate: 6% ÷ 12 = 0.5%
- Total payments: 20 × 12 = 240
- Monthly payment: $1,432
- Total repayment: $1,432 × 240 = $343,680
- Total interest paid: $143,680
Factors That Affect Your Home Loan
Interest Rate — Even a 1% difference can save or cost tens of thousands over the loan life. Always compare rates from multiple lenders.
Loan Term — A longer term means lower monthly payments but much higher total interest. A shorter term saves significantly overall.
Down Payment — The more you pay upfront, the less you borrow and the less interest you pay total.
Credit Score — A higher credit score usually gets you a lower interest rate.
Fixed vs Variable Interest Rate
Fixed Rate: Your rate stays the same for the entire loan period. Predictable and stable. Best when rates are currently low.
Variable Rate: Changes based on market conditions. Can be cheaper initially but carries more risk.
Tips to Reduce Your Loan Cost
- Make extra payments — even one extra per year cuts years off your loan
- Refinance when rates drop significantly
- Choose a shorter term to save on total interest
- Increase your down payment
- Improve your credit score before applying
Use Our Free Loan Calculator
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Try the Free Loan Calculator →Frequently Asked Questions
Rates vary by country and lender. Generally anything below the current market average is considered good. Always compare at least 3 lenders before deciding.
Yes, in most cases. Check if your lender charges an early repayment fee. Paying off early saves significant interest.
A common rule is that your monthly payment should not exceed 28% of your gross monthly income. Use our calculator to find a comfortable amount.