Borrowing Power Calculator (2025)

This tool uses standard mortgage formulas with your inputs. Lenders often apply assessment buffers (e.g., +3% to the rate), minimum expense benchmarks, and income shading (discounts) for variable or bonus income. Treat this as an educational guide; lender outcomes can differ.

Debt-to-Income (DTI) compares total monthly debt repayments (existing + proposed) to total monthly income. As a general guide only: under 30% is typically comfortable, 30–40% moderate, above 40% can be tighter. Actual thresholds vary by lender, product and your scenario.

Serviceability measures monthly living costs plus total debt repayments as a share of income. It complements DTI by including household spending. Lower is better, but suitable levels depend on your budget and risk tolerance.

The stress slider adds the selected percentage to your interest rate and recomputes borrowing power. A higher rate reduces the maximum principal you can support, helping you see sensitivity to rate rises or assessment buffers.

In this version, both gross and net entries are treated as serviceable income for simplicity; no tax calculation is applied. Future versions may include tax estimation and income shading (e.g., counting 70–80% of variable income).

This version supports a single applicant by default and a second applicant on demand. If you need additional co-borrowers, we can extend the form to handle more applicants and aggregate income and liabilities accordingly.