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Our Calculation Methodology
Developed and maintained by a CeMAP-qualified mortgage professional, our tool provides an independent, market-wide view of your borrowing potential across 58 UK lenders.
Why We Are Different
Most online mortgage calculators use a simple income multiple (typically 4.5x) to estimate your borrowing. This gives a rough figure but ignores the significant differences between lenders.
Our system connects to each lender's actual affordability calculator and runs your details through all of them simultaneously. This means you see the real figure each lender would offer, not a generic estimate.
Lender Criteria Mapping
Each of our 58 lenders treats income and expenditure differently. We track over 120 data points per lender to capture these nuances:
- Income multiples — Some lenders offer 4.5x, others stretch to 5.5x or higher for certain professions or income levels.
- Bonus and overtime treatment — Lenders vary from ignoring overtime entirely to counting 100% of the average. We apply each lender's specific policy.
- Self-employed income — Some lenders use the latest year's profits, others average two or three years. Our tool applies the correct method for each.
- Pension and investment income — Treatment varies by lender; some accept it fully, others discount or exclude it.
- Committed expenditure — Credit cards, loans, child maintenance, and other outgoings are factored in using each lender's specific approach.
Interest Rate Stress Testing
Since 2014, the FCA's Mortgage Market Review requires lenders to stress test affordability against potential interest rate rises. Each lender applies its own stress rate, typically 1–3% above their standard variable rate.
Our tool applies the correct stress test for each lender, which is one of the main reasons the same borrower can be offered significantly different amounts by different lenders. You can read more about how this works in our affordability calculation guide.
Data Accuracy and Updates
Mortgage lending criteria change frequently as lenders respond to market conditions, swap rates, and regulatory updates. We maintain accuracy through:
- Direct API connections — Where available, we connect directly to lender affordability calculators for real-time results.
- Regular criteria audits — Our CeMAP-qualified team reviews lender criteria regularly to ensure our data reflects current policies.
- Automated monitoring — We run health checks across all 58 lender connections to detect and resolve issues quickly.
- No commission bias — We are not paid by lenders and do not prioritise results based on commercial relationships. Results are presented neutrally.
Adverse Credit Criteria
For users with adverse credit history, we go beyond basic affordability. Our tool checks each lender's published criteria for six categories: CCJs, defaults, missed payments, bankruptcy, IVA/DRO, and debt management plans. Lenders that do not accept your specific situation are filtered out before the affordability calculation runs.
This includes specialist adverse credit lenders such as Kensington, Pepper, Bluestone, and Precise, who have more flexible criteria than mainstream banks. Learn more on our adverse credit calculator page.
Important Note
This tool provides an expert estimate for information purposes. It is not a mortgage offer or financial advice. A formal Decision in Principle (DIP) from a regulated provider is required for any mortgage application. For personalised mortgage advice, always consult a qualified, FCA-authorised mortgage adviser.
