Two legitimate questions
A lender asks whether the proposed debt meets its credit policy. Your household asks whether the repayment leaves enough for food, transport, care responsibilities, savings and the life you intend to keep living. Those questions overlap, but they are not identical.
Approval calculations often rely on verified income, declared expenditure, existing credit and regulatory criteria. A personal comfort range must go further. It should account for irregular costs, the variability of earnings, planned changes and the amount of monthly breathing room you value.
Build from the residue
Instead of beginning with the largest repayment a calculator permits, begin with the cash margin you refuse to lose. Add realistic ownership costs and test the resulting repayment when rates are less favourable. The property range that remains may be lower, but it is anchored in your household rather than an external ceiling.
Neither figure is a promise. A lender still makes its own decision, while your expenses may change. The useful outcome is a reasoned boundary you can explain before the emotion of an offer takes over.