The Number Banks Do Not Rush to Explain
When you take out a $20,000 car loan at 6% interest over 5 years, your monthly payment is $386.66. Over 60 payments, you will pay $23,199.60 in total. That extra $3,199.60 is the cost of borrowing — the interest. Most people accept this without fully understanding how it is calculated or why paying extra early makes such a large difference.
Understanding amortization — how loans are paid off over time — gives you real control over your financial decisions.
What Amortization Means
An amortized loan is one where each payment covers both the interest that has accrued since the last payment and a portion of the principal (the amount you originally borrowed). In the early stages of a loan, most of each payment is interest. As the loan matures, the interest portion shrinks and the principal portion grows.
This is not a trick or a scam. It is just mathematics. Interest is always charged on the outstanding balance. When the balance is large (early in the loan), interest is large. When the balance is small (late in the loan), interest is small.
The Monthly Payment Formula
For a loan with fixed monthly payments:
M = P × [r(1+r)ⁿ] / [(1+r)ⁿ − 1]
Where:
- M = monthly payment
- P = principal (amount borrowed)
- r = monthly interest rate (annual rate ÷ 12)
- n = total number of payments (years × 12)
For a $20,000 loan at 6% annual interest over 5 years:
- r = 6% ÷ 12 = 0.5% = 0.005
- n = 5 × 12 = 60
- M = 20,000 × [0.005 × (1.005)⁶⁰] / [(1.005)⁶⁰ − 1] = $386.66
How the Split Between Interest and Principal Changes
In the first payment on that $20,000 loan:
- Interest: $20,000 × 0.5% = $100.00
- Principal: $386.66 − $100.00 = $286.66
- Remaining balance: $20,000 − $286.66 = $19,713.34
By payment 30 (halfway through):
- Interest: approximately $50.00
- Principal: approximately $336.66
- Remaining balance: approximately $9,800
By payment 60 (final payment):
- Almost entirely principal, with just a few cents of interest
Why Extra Payments Are So Powerful Early
Every extra dollar you pay toward principal reduces the balance that future interest is calculated on. An extra $100 paid in month 1 saves you more than $100 paid in month 50, because it eliminates interest for many more months.
On the $20,000 loan above, paying an extra $100 per month saves approximately $800 in total interest and pays the loan off about 10 months early. That is a strong return for a relatively small extra effort.
Comparing Loan Offers
When comparing loans, look at three numbers, not just the monthly payment:
- Total interest paid: this is the true cost of the loan
- Annual Percentage Rate (APR): includes fees and gives a truer picture than nominal interest rate
- Loan term: a longer term means lower monthly payments but higher total cost
A 5-year loan at 6% and a 7-year loan at 5% might have similar monthly payments but very different total costs. Running both through a loan calculator before signing reveals the real difference.
How to Use the Toobits Loan Calculator
Enter the loan amount, annual interest rate, and term in months. The calculator shows your monthly payment, total amount paid across all payments, and total interest paid. Adjust any input and all numbers update instantly — making it easy to compare different loan amounts, rates, and terms side by side before making a decision.