Almost everyone shopping for a mortgage starts by ranking offers on the interest rate, lowest first. It feels like the obvious move, and lenders know it — which is why the rate is the biggest number in every advertisement and the fees are in the small print. The rate matters enormously, but on its own it can point you at the more expensive loan. This guide walks through what to compare instead, in the order that actually affects what leaves your bank account.
Start with the total cost, not the monthly payment
The monthly payment is the figure most people fixate on, because it is the one they feel every month. But two loans with an identical monthly payment can differ by tens of thousands over their lifetime, because the payment says nothing about how long you keep making it. A longer term shrinks the monthly figure and inflates the total. The number that tells the truth is the total interest paid across the whole loan.
Consider a $280,000 loan at 6.5%. Over 30 years the monthly principal and interest is around $1,770, and the total interest comes to roughly $357,000 — more than the amount you borrowed. Shorten the same loan to 20 years and the monthly payment rises to about $2,090, but the total interest falls to around $221,000. That is a $136,000 difference for the same debt at the same rate, driven entirely by time — the same force, working against you, that builds wealth when you are saving. When you compare offers, put the total interest side by side. Our mortgage calculator shows it on every calculation.
The rate and the APR are not the same thing
The interest rate is the cost of borrowing the money. The APR, or annual percentage rate, folds in the compulsory fees as well — arrangement fees, some closing costs, and certain insurance — and expresses the whole thing as a single yearly percentage. This is why a loan with a tempting 6.1% rate and $6,000 in fees can be more expensive than a plain 6.4% loan with no fees at all.
The APR is designed to make that comparison possible, but it has a blind spot: it assumes you keep the loan for its full term. If you expect to move or refinance in five years, a large upfront fee is spread over five years in reality, not thirty, which makes it hurt far more than the APR suggests. Use the APR as a first filter, then think about how long you actually intend to hold the loan.
List every fee, then decide who really pays
Fees hide in a surprising number of places: arrangement or origination fees, valuation and survey costs, legal fees, broker fees, and sometimes a charge simply for booking a rate. Ask each lender for a full breakdown in writing. Then look at which fees can be added to the loan and which must be paid upfront in cash.
Rolling fees into the loan feels painless because you do not write a cheque, but you then pay interest on those fees for the entire term. A $3,000 fee added to a 30-year loan at 6.5% costs far more than $3,000 by the time the loan ends. Paying fees upfront, where you can afford it, is almost always cheaper.
Fixed, variable, and the question of certainty
A fixed rate stays the same for a set period, giving you a payment you can plan around. A variable or adjustable rate moves with the market, which can be cheaper when rates fall and painful when they rise. Comparing a fixed offer against a variable one is not just about which number is lower today; it is about how much certainty is worth to you.
If your budget has no slack, the value of a payment that cannot rise is high, and a slightly higher fixed rate can be money well spent. If you have room to absorb an increase and expect rates to fall, a variable deal may win. What you should never do is compare a two-year introductory variable rate against a ten-year fixed rate as if they were the same product. Line up like with like: compare the fixed period against an equivalent commitment, and ask what the variable rate reverts to when the introductory period ends.
The deposit changes everything above it
The size of your deposit does more than reduce the amount you borrow. It moves you between lender risk bands, and those bands carry different rates. Crossing below 20% down usually triggers mortgage insurance, an extra monthly cost that protects the lender, not you, and does nothing to reduce your balance. Crossing below 10% often means a noticeably higher rate on top.
This means a small increase in your deposit can pay for itself twice: once by shrinking the loan, and again by unlocking a lower rate on the whole thing. Before you compare offers, find out where the deposit thresholds sit for each lender, because an offer that looks worse at your current deposit may become the best one if you can add a little more.
Watch for early repayment charges
Many mortgages penalise you for overpaying or clearing the loan early during the fixed period. If there is any chance you will move, refinance, or come into money you want to put towards the balance, an early repayment charge can wipe out the savings from a lower rate. Two otherwise identical offers can differ sharply on this single clause, and it rarely appears in the headline comparison. Ask for it explicitly.
A practical way to rank offers
Put the offers in a simple table and fill in five columns for each: the monthly payment, the total interest over the term you actually expect to hold the loan, the total fees split into upfront and rolled-in, whether the rate is fixed and for how long, and the early repayment terms. Ranking on that table rather than on the rate alone will often reorder the offers, and the one that looked second or third on rate frequently turns out to be the cheapest overall.
Run each scenario through the mortgage calculator to see the monthly payment and total interest for the price, deposit and rate on offer, and use the loan calculator if you want to model overpayments. The lender's own official illustration is always the final word, but going in with your own numbers means you will spot a bad deal before you sign it.
The one-sentence version
Compare mortgages on the total cost over the time you will really keep the loan, with every fee counted and the certainty of the rate weighed against your budget — not on the advertised rate, which is chosen to win exactly the comparison you should not be making.