Mortgage in Principle Calculator — Which Lenders Would Say Yes?

A mortgage in principle (MIP) is a lender's conditional statement of how much they'd likely lend you, based on a quick review of your income, outgoings and credit. It goes by several names — agreement in principle (AIP), decision in principle (DIP), a mortgage promise, or sometimes informally "mortgage pre-approval" — and they all mean the same thing. Some lenders issue a DIP certificate you can show an estate agent as proof. Most lenders issue a real AIP or DIP online in 5 to 15 minutes, since it only checks a summary of your finances rather than full documentation.

The important words are a lender's. An AIP isn't a market-wide verdict; it's one company's answer, using one company's rulebook. That's why this mortgage in principle calculator doesn't hand you a single number — it shows a spread of answers across different lender types, which is far closer to what happens in practice.

If you just want a broad "how much could I borrow" figure, use the mortgage affordability calculator. Come here when you want to know who would actually approve you, and what's standing in the way.

Two applicants with the same £60,000 household income can be offered £190,000 by one lender and £330,000 by another. Nothing about them changed — only the rulebook did. Four levers do most of the work:

1. Income multiple. Typically 4× to 4.5×, but 5× to 5.5× exists for higher earners, certain professions and some first-time buyer schemes. That alone is a £90,000 swing on a £60,000 income.

2. Maximum LTV. A lender capping at 85% simply cannot lend you more than your deposit supports, however high your income. With a £40,000 deposit, an 85% cap means a hard ceiling of about £227,000 — the income multiple never even comes into play.

3. Minimum income thresholds. The generous 5.5× products usually require a household income floor (often around £40,000) and a 10% deposit. Below that, you're back to 4.5×.

4. Credit and employment policy. One missed payment closes some doors entirely and none at others. Under two years of self-employed accounts rules out most high-street lenders — but not specialists.

Your in-principle figure is always the lower of the income cap and the LTV cap. The calculator above tells you which one is binding for each lender, so you know whether to save more deposit or earn more income.

Most lenders use a soft credit search for a mortgage in principle. It isn't visible to other lenders and has no impact on your score, so you can safely compare a few.

Some use a hard search, which is recorded on your file. Several hard searches in a short window can look like distress borrowing and dent your score — which is precisely why it pays to match yourself to likely-yes lenders before applying. Ask which type they use, every time.

If you're self-employed, our self employed mortgage calculator shows how each trading type is assessed. If family can help, the guarantor mortgage calculator shows how much a JBSP arrangement adds.

You and a partner earn £35,000 and £25,000 (£60,000 combined), have a £40,000 deposit and £200/month of commitments. Clean credit, both employed, first-time buyers.

Your assessed income after commitments is £57,600. Run that through the six profiles and the answers scatter:

The first-time buyer boost lender says yes at 5.5× — around £316,800, and your deposit sits comfortably inside their 90% LTV cap. The high-street standard lender offers about £259,000 at 4.5×. The cautious lender offers £230,000 at 4×. The professional lender declines outright — your household income is below their £75,000 floor. The self-employed specialist isn't relevant to you, and the adverse-credit specialist would lend, but on terms you don't need.

Same couple, same day. An £87,000 spread between the best and worst answer, and one flat decline. That gap is the entire reason to check who says yes before you apply — not just how much.

Official sources & further reading: read the buying-a-home guides at MoneyHelper, explore government schemes on GOV.UK, and verify any adviser on the FCA register. Browse every tool on the mortgage calculators homepage.