Borrowing Power Calculator for Buying Together
See roughly how much you and a co-buyer could borrow together - and the catch the bank's calculator leaves out.
Two people buying together can usually borrow more than either alone, because a lender assesses your combined income - but you're each liable for the whole loan. In Australia many lenders count only the two highest incomes; in the US the lowest median credit score among you often sets the rate.
Last updated July 2026
The reason most people buy a home with someone else is simple: two incomes borrow more than one. This calculator gives you a rough idea of how much a group could borrow together, from your combined income, your living costs and the rate - so you can sanity-check what you might afford before you talk to a broker.
It's an estimate, not a pre-approval. Lenders each have their own rules, and the real figure depends on things this tool doesn't ask for. Treat it as a starting point for the conversation, not a promise.
How this calculator works
- Enter each buyer's income and any existing loan or card repayments, plus the rate and term, then pick your market with the AU/US toggle.
- In Australia the calculator takes your net income minus living costs and debts, then assesses it at your rate plus a 3% buffer - the serviceability cushion APRA requires lenders to apply. In the US it applies a debt-to-income limit (around 43%, and up to ~45-50% with strong credit) to your gross income at the note rate, then keeps back part of the housing budget for property taxes and insurance.
- Either way it works backwards to the loan that budget could support. It's a rough estimate only - a lender or broker gives you the real number.
A worked example
In Australia, two buyers earning $100,000 and $80,000 with about $3,000 a month in living costs and no other debts come out around $1 million, assessed at their rate plus the 3% buffer - though a lender's own expense benchmarks usually pull the real figure lower.
In the US, the same incomes at a 43% debt-to-income limit and a 6% note rate - with roughly a fifth of the housing budget set aside for property taxes and insurance - land closer to $860,000. Either way the number moves fast: a $500-a-month car payment can knock tens of thousands off what you'll be offered.
Australia and the United States
The math is the same wherever you buy. For country-specific tax and legal detail - stamp duty and CGT in Australia, closing costs and capital gains in the US - read the guide for Australia or the United States.
Good to know
- A rough estimate only - not a pre-approval or a lending decision. Every lender assesses differently.
- AU mode uses resident tax rates and a 3% APRA serviceability buffer. US mode uses a back-end debt-to-income cap (default 43%) at the note rate, reserving about a fifth of the housing budget for taxes and insurance; it does not apply the ~28% front-end housing ratio some lenders also use.
- It doesn't account for dependants, credit scores, property taxes, HOA or insurance, student/HELP debt, or a lender's own expense benchmarks.
- Educational estimate - not legal, credit or financial advice.
Frequently asked questions
How much can two people borrow together?
Usually more than either could alone, because the lender adds your incomes - though not simply double. Your combined borrowing power is your incomes minus living costs and existing debts, all assessed at the rate plus a buffer. This tool gives you a rough combined figure.
Do lenders count both incomes when you buy with a friend?
For a couple, generally yes. For three or more borrowers, many lenders count only the two highest incomes, so adding a third buyer doesn't always add much borrowing power. Ask the lender or broker how they'll treat your particular group.
Are we each responsible for the whole loan?
On a standard joint mortgage, yes - each borrower is liable for the entire debt, not just their share. If one person can't pay, the lender can pursue the others for the full amount. It's the single most important thing to understand before co-borrowing.
How do US and Australian lenders assess borrowing power differently?
Australian lenders test you at your rate plus a 3% buffer against your income after living costs; US lenders apply a debt-to-income cap (commonly around 43%) at the note rate. This tool switches methods with the AU/US toggle - both are conservative estimates, not approvals.
Does buying with a friend really increase how much we can borrow?
Usually yes - the lender adds your incomes, so a couple or a pair of friends can borrow more than either alone. But you're each fully liable for the loan, and in the US the lowest median credit score in the group can raise the rate for everyone, so more borrowers isn't always simply more borrowing.