How Your First Mortgage Payment Splits: A Dollar-by-Dollar Look at Amortization
You take possession in September. The lawyer emails a breakdown of your closing costs, and buried halfway down the spreadsheet is the adjustment for property taxes, land transfer, and your first mortgage payment. The payment figure is $2,847.33. Most people assume that means they now own $2,847.33 more of their house.
They don't. Not even close.
The opening math
On a $650,000 purchase in Ottawa with 10% down, you're borrowing $585,000. At 5.24% on a 25-year amortization, the monthly payment is $3,513. Of that first $3,513, roughly $2,558 goes to interest. The remaining $955 goes to principal.
You are renting the bank's money at a cost of $2,558 that month. The $955 is the portion you're actually buying back.
The reason the interest portion is so high has nothing to do with penalty rates or origination fees. It's arithmetic. Interest is calculated on the outstanding balance. On day one, you owe the full $585,000. A 5.24% annual rate, compounded semi-annually under Canadian law, translates to roughly 0.437% monthly. Apply that to $585,000 and you get $2,558. What's left over after paying that cost is what reduces the balance.
Why the split moves so slowly
Month two, the balance is now $584,045. The interest cost drops to $2,554. Four dollars. The principal portion rises to $959. Four dollars.
By month twelve, you've made $42,156 in total payments. Of that, $30,312 was interest. You've reduced the loan balance by $11,844. Less than a third of what you paid went toward ownership.
This isn't a product design flaw. It's the structure of compound interest working in reverse. The bank's cost to lend you $585,000 doesn't shrink until the balance shrinks, and the balance shrinks slowly because most of the payment is covering the cost, not the balance itself.
The visible shift doesn't happen until year ten. At that point, the balance has dropped to around $430,000, the interest portion of each payment has fallen below $2,000, and more than half of what you're paying finally goes to principal. On a 25-year amortization, you hit the break-even point somewhere between month 120 and 140, depending on the rate.
What this means for prepayment
A $5,000 lump sum applied in year one eliminates $5,000 of balance immediately. That $5,000 would have cost you roughly $6,200 in interest over the remaining 24 years. You just bought a guaranteed, tax-free return equal to your mortgage rate.
The same $5,000 applied in year eighteen saves far less, because there are only seven years of compounding left to eliminate. The dollar amount is the same. The value isn't.
Most lenders in Ontario and BC allow 10% to 20% of the original principal as an annual prepayment. On a $585,000 mortgage, that's $58,500 to $117,000 per year. Almost no one uses it. The reason is usually cash flow, which is rational. But the math says that dollar-for-dollar, there is no better guaranteed return than killing mortgage interest early.
The compounding trick nobody mentions
Fixed-rate mortgages in Canada are compounded semi-annually by law. Variable-rate mortgages are often compounded monthly. That difference changes the effective rate. A 5.24% fixed, compounded semi-annually, is slightly cheaper over the life of the loan than a 5.24% variable compounded monthly. Not by much. By enough.
If you're comparing a fixed and a variable at the same posted rate, the fixed is mathematically cheaper on interest alone, setting aside rate risk. Almost no one pricing mortgages mentions this because almost no one prices mortgages on the compounding basis. They price on the rate and the payment, which hides the actual cost structure.
The first payment feels like progress. It is progress, just not the amount you think. You're buying $955 worth of house and paying $2,558 to do it. By month sixty, you're buying $1,150 worth of house and paying $2,363 to do it. The ratio improves. Slowly.
Understanding that ratio changes which financial moves make sense and which ones don't.
You take possession in September. The lawyer emails a breakdown of your closing costs, and buried halfway down the spreadsheet is the adjustment for property taxes, land transfer, and your first mortgage payment. The payment figure is $2,847.33. Most people assume that means they now own $2,847.33 more of their house.
They don't. Not even close.
The opening math
On a $650,000 purchase in Ottawa with 10% down, you're borrowing $585,000. At 5.24% on a 25-year amortization, the monthly payment is $3,513. Of that first $3,513, roughly $2,558 goes to interest. The remaining $955 goes to principal.
You are renting the bank's money at a cost of $2,558 that month. The $955 is the portion you're actually buying back.
The reason the interest portion is so high has nothing to do with penalty rates or origination fees. It's arithmetic. Interest is calculated on the outstanding balance. On day one, you owe the full $585,000. A 5.24% annual rate, compounded semi-annually under Canadian law, translates to roughly 0.437% monthly. Apply that to $585,000 and you get $2,558. What's left over after paying that cost is what reduces the balance.
Why the split moves so slowly
Month two, the balance is now $584,045. The interest cost drops to $2,554. Four dollars. The principal portion rises to $959. Four dollars.
By month twelve, you've made $42,156 in total payments. Of that, $30,312 was interest. You've reduced the loan balance by $11,844. Less than a third of what you paid went toward ownership.
This isn't a product design flaw. It's the structure of compound interest working in reverse. The bank's cost to lend you $585,000 doesn't shrink until the balance shrinks, and the balance shrinks slowly because most of the payment is covering the cost, not the balance itself.
The visible shift doesn't happen until year ten. At that point, the balance has dropped to around $430,000, the interest portion of each payment has fallen below $2,000, and more than half of what you're paying finally goes to principal. On a 25-year amortization, you hit the break-even point somewhere between month 120 and 140, depending on the rate.
What this means for prepayment
A $5,000 lump sum applied in year one eliminates $5,000 of balance immediately. That $5,000 would have cost you roughly $6,200 in interest over the remaining 24 years. You just bought a guaranteed, tax-free return equal to your mortgage rate.
The same $5,000 applied in year eighteen saves far less, because there are only seven years of compounding left to eliminate. The dollar amount is the same. The value isn't.
Most lenders in Ontario and BC allow 10% to 20% of the original principal as an annual prepayment. On a $585,000 mortgage, that's $58,500 to $117,000 per year. Almost no one uses it. The reason is usually cash flow, which is rational. But the math says that dollar-for-dollar, there is no better guaranteed return than killing mortgage interest early.
The compounding trick nobody mentions
Fixed-rate mortgages in Canada are compounded semi-annually by law. Variable-rate mortgages are often compounded monthly. That difference changes the effective rate. A 5.24% fixed, compounded semi-annually, is slightly cheaper over the life of the loan than a 5.24% variable compounded monthly. Not by much. By enough.
If you're comparing a fixed and a variable at the same posted rate, the fixed is mathematically cheaper on interest alone, setting aside rate risk. Almost no one pricing mortgages mentions this because almost no one prices mortgages on the compounding basis. They price on the rate and the payment, which hides the actual cost structure.
The first payment feels like progress. It is progress, just not the amount you think. You're buying $955 worth of house and paying $2,558 to do it. By month sixty, you're buying $1,150 worth of house and paying $2,363 to do it. The ratio improves. Slowly.
Understanding that ratio changes which financial moves make sense and which ones don't.
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