What it means
A mortgage is simply a long-term loan secured against property, and the words "fixed rate" describe how the interest on it is charged. The lender agrees a percentage at the outset and cannot change it during the fixed period, however far the central bank moves its own rate.
For a business, the appeal is a predictable cash outflow. A company that owns its premises on a fixed rate knows its occupancy cost years ahead, which makes budgeting, covenant testing and cash flow forecasting far easier than with a loan whose rate moves every quarter.
The repayment is calculated so that equal instalments cover both interest and principal across the full term, a structure called amortisation. Early payments are mostly interest and later ones mostly principal, which is why overpaying in year two saves far more total interest than overpaying in year twenty.
The trade-off is that a fixed rate is usually priced slightly above the equivalent variable rate, because the lender is absorbing the risk that rates rise. If rates fall instead, the borrower is stuck, and exiting the deal early often triggers an early repayment charge of roughly 1% to 5% of the outstanding balance.
Hybrid products blur the line, so read the small print carefully. A five-year fix on a 25-year term is fixed only for the first five years, after which the loan reverts to the lender's standard variable rate, so the fixed period rather than the loan term is the real planning horizon.
In practice
Real-world examples.
Example
A dental practice buys its own surgery for $600,000 with a $450,000 fixed rate mortgage at 5.5% over 20 years. The partners can now quote a fixed monthly premises cost in their five-year plan, which they could not do while renting with annual rent reviews.
Example
A family bakery refinances a variable rate loan into a 10-year fixed rate deal just before a run of central bank rate rises. Its payment stays flat while a competitor on a tracker sees monthly interest climb by roughly a third, and the bakery holds its pricing steady for a full season.
Example
A property investor takes a two-year fixed rate on a rental flat, expecting rates to fall. When the fix ends, rates have risen instead, and the reversion to the standard variable rate lifts the payment by $340 a month, wiping out most of the rental profit.
Think of it
“Fixed rate mortgage has constant interest-same payment throughout.
Formula
Calculation
Monthly payment = L x r / (1 - (1 + r)^-n), where L is the loan amount, r is the monthly interest rate (annual rate divided by 12) and n is the total number of monthly payments.
Take a $300,000 loan fixed at 6% for 30 years. The monthly rate r is 0.06 / 12 = 0.005, and n is 30 x 12 = 360 payments.
(1 + 0.005)^360 = 6.0226, so (1 + r)^-n = 1 / 6.0226 = 0.16604.
The denominator is 1 - 0.16604 = 0.83396, and the numerator is $300,000 x 0.005 = $1,500.
Monthly payment = $1,500 / 0.83396 = $1,798.65.
Across the full term the borrower pays $1,798.65 x 360 = $647,514, of which $300,000 is the original loan and $347,514 is interest. That interest figure is fixed on day one, which is exactly the certainty the borrower is paying for.Case study
Seen in the real world.
This is an illustrative, entirely fictional example. Harbourline Physiotherapy, an invented three-clinic group, had spent nine years renting its main site before the landlord offered to sell. The founders borrowed $480,000 on a 25-year mortgage fixed at 5.75% for the first 10 years, giving a payment of just over $3,000 a month.
The finance director's argument to the board was not that fixing was cheaper. On the day of drawdown the variable alternative was 0.4 percentage points lower, so fixing cost the clinic around $1,900 more in the first year. What fixing bought was a premises line in the budget that would not move for a decade, which let the group commit to hiring two extra physiotherapists.
Three years later, market rates had risen above the fixed rate and the decision looked prescient, but the board minutes deliberately recorded it as risk management rather than a forecast. Had rates fallen instead, the clinic would have paid a modest premium for certainty and still been able to plan, which was the point.
Watch out
Common mistakes.
- Believing a fixed rate mortgage means a fixed total monthly bill. Insurance, service charges and, in many escrow arrangements, property taxes still move, so the all-in payment can rise even when the interest rate cannot.
- Assuming the rate is fixed for the whole loan term. Most deals outside the US fix the rate for an initial period only, and the reversion rate afterwards is usually much higher.
- Comparing deals purely on the headline rate. Arrangement fees, valuation fees and early repayment charges can easily outweigh a 0.1 percentage point rate difference on a smaller loan.
Questions
People also ask.
Is a fixed rate always more expensive than a variable rate?
Not always, but it usually starts higher because the lender is being paid to carry the risk that rates rise during the fixed period.
Can I overpay a fixed rate mortgage?
Most lenders allow overpayments of up to around 10% of the balance a year without penalty, and anything above that typically attracts an early repayment charge.
What happens when the fixed period ends?
The loan normally reverts to the lender's standard variable rate, so borrowers should start shopping for a new deal several months before the fix expires.
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