Check what the calculator includes, such as your income, outgoings, deposit, mortgage term, interest rate and whether repayments are fixed or variable. Ask whether fees, insurance, taxes and possible rate rises are included, as different calculators make different assumptions. Try several scenarios, including a larger deposit, a shorter term and higher interest rates, to see how repayments might change. The result is only an estimate, so an FCA-authorised mortgage adviser or lender would need to assess your individual circumstances before confirming affordability.