A mortgage is the biggest loan most people ever take on, yet how it actually works is often only half understood. This guide explains how mortgages work in plain English: the deposit and loan, interest and the rate, how you repay, the term, and what happens when deals end, so you can borrow with confidence.
What a mortgage is
A mortgage is a loan used to buy property, secured against that property. Because it is secured, the lender can repossess and sell the home if you do not keep up repayments, which is why a mortgage usually has a much lower interest rate than unsecured borrowing. You borrow a large sum, repay it over many years with interest, and once it is fully repaid, you own the home outright.
The deposit and the loan
You put down a deposit, a percentage of the price from your own funds, and borrow the rest as the mortgage. The size of your deposit relative to the price is your loan-to-value, which affects the rates you are offered, as our guide to loan-to-value explains. A bigger deposit means a smaller loan, lower loan-to-value and usually better rates, so the deposit matters a great deal.
Interest and the rate
The lender charges interest on what you borrow, expressed as a rate. The rate can be fixed for a period or variable, and it determines much of your monthly payment, as our guide to fixed versus variable explains. Even small differences in the rate make a big difference over the life of a mortgage, which is why comparing rates carefully is so important when choosing a deal.
How you repay
Most mortgages are repayment, meaning each monthly payment covers the interest plus a little of the capital, so the balance gradually falls and the loan is cleared by the end of the term. Some, especially buy-to-let, are interest-only, where you pay just the interest and repay the capital separately, as our guide to repayment versus interest-only explains. Repayment steadily builds your ownership of the home.
The mortgage term
The term is how long you take to repay the mortgage, commonly 25 years but often anywhere from around 5 to 40 years. A longer term lowers monthly payments but means more interest overall, while a shorter term costs more each month but less in total, as our guide to the mortgage term explains. Choosing a term that balances affordable payments against total cost is an important decision.
Your monthly payments
Your monthly payment depends on the amount borrowed, the interest rate, the term, and whether the mortgage is repayment or interest-only. On a repayment mortgage, early payments are mostly interest, with more going to capital over time. Understanding what drives your payment, the loan, rate and term, helps you see how choices like a bigger deposit or shorter term change what you pay each month.
Deals and the standard variable rate
Most people take an initial deal, such as a fixed or tracker rate, for a set period, after which the mortgage reverts to the lender's standard variable rate, which is usually higher, as our guide to the standard variable rate explains. This is why people remortgage when their deal ends, switching to a new deal to avoid the costly standard variable rate and keep their payments down.
Your home is at risk
Because a mortgage is secured on your home, it is essential to keep up the payments, as the home can be repossessed if you do not. Lenders assess affordability before lending to reduce this risk, but it remains a serious commitment. Borrowing an amount you can comfortably afford, now and if rates rise, and keeping a buffer, helps protect your home and gives you peace of mind.
Getting a mortgage
To get a mortgage, you apply to a lender, who assesses your income, outgoings, credit history and the property, then decides how much to lend and on what terms. If approved, you receive a mortgage offer setting out the loan, rate and conditions. The lender values the property to confirm it is suitable security. Understanding this process helps you prepare and improves your chances of approval at a good rate.
The mortgage in principle
Before house-hunting, many people get a mortgage in principle, an indication from a lender of how much they could borrow, based on initial checks, as our guide to the mortgage in principle explains. It is not a full offer, but it shows sellers you are a serious buyer and focuses your search on affordable homes. Getting one early is a sensible first step toward a mortgage.
Fees to budget for
Mortgages can come with fees, such as an arrangement or product fee, a booking fee, and a valuation fee, as our guide to mortgage fees explains. These add to the cost of a deal, so a low rate with a high fee is not always cheaper than a slightly higher rate with no fee. Factoring fees into your comparison gives a truer picture of which mortgage is best value.
Comparing the true cost
When comparing mortgages, look beyond the headline rate to the overall cost, including fees and how long the deal lasts, as our guide to comparing mortgages explains. A deal that looks cheapest on rate may not be once fees are added, especially on a smaller mortgage. Comparing the total cost over the deal period helps you choose the mortgage that genuinely costs you least.
Using a broker
Many people use a mortgage broker, who can search the market, recommend suitable deals, and handle much of the application. A broker can be especially helpful if your circumstances are complex or you want help comparing the whole market. Given how much a mortgage costs over its life, getting the right one, with a broker's help if you wish, is well worth the effort of doing properly.
Affordability and stress testing
Before lending, a lender checks affordability, examining your income and outgoings and stress testing whether you could still pay if rates rose. This determines how much you can borrow, as our guide to how much you can borrow explains. Borrowing within, rather than at the very top of, what you are offered leaves a buffer for rate rises and life changes, which is a sensible way to keep a mortgage comfortable.
Understanding these building blocks, the deposit, the loan, the rate, the term and how you repay, gives you the foundation to compare deals and choose a mortgage that suits your circumstances, rather than simply taking the first one offered.
For most people, a mortgage is a long-term commitment that will be part of their finances for decades, so it is well worth taking the time to understand how it works and to choose a deal, term and structure that genuinely fit your life rather than simply accepting whatever is first put in front of you.
In short
A mortgage is a loan secured on property: you put down a deposit, borrow the rest, and repay it with interest over a term, usually around 25 years. Most are repayment, gradually clearing the loan, while some are interest-only. The rate can be fixed or variable, and deals revert to the higher standard variable rate when they end. Because your home is at risk, borrow affordably and keep up payments.
Where to get help and next steps
Read our guides to fixed versus variable rates, repayment versus interest-only, and offset mortgages. This is general information, not mortgage or financial advice.