Car Loan Amortization Calculator: How Your Payment Splits Between Principal and Interest

Most people look at their car loan statement, see the payment amount, and never ask how that number splits between principal and interest. It's worth ten minutes of your time, because the split changes every single month you have the loan, and understanding it tells you exactly when extra payments actually help.

We've already covered the basics of how amortization schedules work in Canada. This post is different. Instead of defining terms, we're going to build one by hand, using real numbers, so you can see exactly where each dollar of your payment goes.

The formula behind every car loan payment

Every fixed-rate car loan uses the same math to figure out your monthly payment. In plain language: the lender takes your loan amount, applies your monthly interest rate, and spreads the whole thing evenly across every payment so that the balance hits zero on the exact month your term ends.

The formula itself looks like this:

M = P × [r(1+r)^n] / [(1+r)^n − 1]

Where M is your monthly payment, P is the amount you borrowed, r is your monthly interest rate (annual rate divided by 12), and n is the number of monthly payments in your term. If you want the full breakdown of each variable, we walked through it in our car loan calculator formula guide.

What that formula doesn't show you, on its own, is what happens inside each payment. That's where amortization comes in.

A worked example: $28,000 over 60 months

Let's use a sample loan. These numbers are illustrative only, not a quoted rate, but they're realistic enough to show you how the math actually behaves.

Say you finance $28,000 at 7.49% over 60 months (five years). Run that through the formula above and you get a monthly payment of roughly $560.70. Over five years, that's $33,642 total, meaning about $5,642 goes to interest and the rest pays down the car itself.

Now here's the part your loan statement doesn't spell out for you. That $560.70 isn't split the same way every month. In month one, interest eats a much bigger chunk of it than it will in month 59.

Here's roughly how it plays out, year by year:

Year 1: you start owing $28,000 and end the year at about $23,193. Of the $6,728 you paid that year, roughly $4,807 went to principal and $1,921 went to interest.

Year 2: balance drops from $23,193 to about $18,029. Same $6,728 paid, but now $5,164 is principal and only $1,564 is interest.

Year 3: balance goes from $18,029 to roughly $12,459. Principal share climbs to about $5,570, interest falls to $1,158.

Year 4: balance drops to around $6,459. You're now paying about $6,000 toward principal and just $728 in interest.

Year 5: the loan clears. Final year principal is about $6,459, interest is down to roughly $269.

Notice the pattern. Your payment never changes, but the mix inside it shifts every year, more toward principal, less toward interest, as the loan winds down.

Why interest gets front-loaded

This isn't a trick lenders play on you. It's just how interest works on a shrinking balance. Interest for any given month is calculated on whatever you still owe, not on the original loan amount. In month one, you owe the full $28,000, so interest that month is the biggest it'll ever be. Each payment chips away at the balance, so the next month's interest charge is a little smaller, which frees up a little more of your fixed payment to go toward principal instead.

It compounds on itself. Lower balance means lower interest means more principal paydown means an even lower balance the following month. That's why the second half of a loan pays down so much faster, in terms of balance, than the first half, even though every payment is identical in size.

If you want a step-by-step walkthrough of computing your own payment before you even sign paperwork, this guide covers that in more detail.

What a bigger down payment or shorter term actually saves you

Down payments and loan terms both change your amortization schedule, but they work differently, and it helps to see the numbers side by side.

Adding a down payment

Take that same $28,000 loan and knock $3,000 off the top with a down payment, leaving $25,000 financed at the same 7.49% over 60 months. Your payment drops to about $500.60 a month, and total interest over the life of the loan falls to roughly $5,036, down from $5,642. You save about $606 in interest just by shrinking the amount you're borrowing in the first place, on top of the $3,000 you didn't have to finance at all.

Shortening the term

Now keep the loan amount at $28,000 but compress the term to 36 months instead of 60. Your monthly payment jumps to roughly $870.80, a lot more than $560.70. But total interest drops to about $3,349, a savings of nearly $2,300 compared to the five-year term.

That's the trade-off in a nutshell. Shorter terms cost less overall but demand more room in your monthly budget. Longer terms ease the monthly hit but cost more in total interest, because the balance sits higher for longer and keeps generating interest charges month after month.

How extra payments reshape the schedule

This is where amortization math actually becomes useful, not just interesting. Because every extra dollar you put toward principal today skips ahead in the schedule, it wipes out interest that would have been charged on that dollar for every remaining month of the loan.

Back to our original $28,000 example. Say that after your first 12 payments, you get a tax refund and put $2,000 of it straight onto the loan's principal. Your balance drops from $23,193 to $21,193 in one move, but your monthly payment stays at $560.70.

Because the payment doesn't change, that lump sum doesn't lower your bill, it shortens your loan. Instead of 48 payments remaining, you're now looking at roughly 43. You finish the loan about five months early, and you cut total interest paid by around $800 compared to sticking with the original schedule.

That's the mechanic worth remembering: a lump sum applied to principal, rather than skipped or spread across future payments, removes interest on every month it would otherwise have accrued. Even smaller, regular extra payments compound the same way over time. We go deeper into strategies and any lender restrictions to check for in our guide to paying off a car loan early in Canada.

Building your own amortization breakdown

You don't need special software to check this yourself. Once you know your loan amount, rate, and term, you can calculate your payment with the formula above, then work out each month's interest by multiplying your current balance by your monthly rate. Whatever's left of the payment after that is principal. Subtract that from your balance, and you've got next month's starting point. Repeat that for the length of your term and you've built a full schedule by hand.

It's tedious past a few months, which is exactly why most people use a spreadsheet or an online calculator instead. But doing it manually once, even just for the first three or four months, makes the shape of the whole thing click in a way that staring at a payment amount never will.

Two things worth checking before you commit to any loan: ask whether interest compounds daily or monthly, since that changes the precise numbers slightly, and confirm there's no prepayment penalty if you plan on making extra payments down the road.

If you're ready to see what a real amortization schedule would look like for your situation, rather than an illustrative one, check your rate and get pre-approved with Auto Lending Canada. It only takes a few minutes, and you'll see actual numbers based on your credit profile and the vehicle you're financing, not estimates.