Debt-to-Income Ratio for a Personal Loan in Australia: How It's Calculated

Your debt-to-income ratio — DTI — is the percentage of your gross monthly income that's already committed to debt repayments.

Lenders calculate it as `(total monthly debt repayments ÷ gross monthly income) × 100`, and the line most of them draw is 50%. Stay under it and DTI isn't holding you back. Cross it and your application moves into the Possible — lender dependent band, no matter how strong the rest of your profile looks.

The part that trips people up: DTI doesn't count what most people think of as "living costs." Your rent isn't in there. Your groceries aren't in there. What is in there is every debt repayment you're carrying, the loan you're currently applying for, and — this is the one that catches people out — 3.5% of your total credit card limit every month, whether you use the card or not.

The short answer

Key takeaway: DTI is a debt check, not a living-costs check. It answers one question — how much of your income is already spoken for by debt — and it answers it before your rent, your groceries, or your dependents ever enter the picture.

How DTI is actually calculated

`DTI (debt-to-income ratio)` — the percentage of your gross monthly income already committed to debt repayments — is worked out like this:

``` DTI (%) = (Total Monthly Debt Repayments ÷ Gross Monthly Income) × 100 ```

Gross monthly income is your gross annual income divided by 12 — before tax, not your take-home pay. That's a different number to the one used in the affordability check, which uses your net (after-tax) income instead. Two separate formulas, two separate income figures — it's worth keeping that straight.

What counts as a debt repayment

What's left out

Rent, your HEM living expenses, utility bills, and high-risk spending like ATM withdrawals, gambling, or crypto purchases don't appear anywhere in this formula. They're real costs, and lenders absolutely check them — just in a different part of the assessment, called affordability, not here.

Why the credit card line catches people out: a lender doesn't ask what you currently owe on a card. It assesses what you *could* owe, because a credit limit is a standing offer of credit you can draw on at any time. A $15,000 limit is treated as a $525-a-month obligation whether you've spent a dollar on it or not. If you're carrying a card you never use, see Does Your Credit Card Limit Affect Your Personal Loan Application? for how much that alone can move your DTI.

A worked example — and how quickly it climbs

Take someone on a gross annual income of $72,000 — gross monthly income of $6,000.

Starting position — one car loan, one credit card, applying for a personal loan:

• Car loan repayment: $400/month
• Credit card limit $10,000 → assessed at 3.5% = $350/month
• BNPL repayments: $150/month
• Proposed new personal loan repayment: $600/month

``` Total debt repayments = $400 + $350 + $150 + $600 = $1,500 DTI = ($1,500 ÷ $6,000) × 100 = 25.0% ```

At 25%, this passes comfortably — well under the 50% line.

Add an existing personal loan and a bigger credit card limit:

• Existing personal loan repayment: $650/month
• Credit card limit increased to $20,000 → assessed at 3.5% = $700/month

``` Total debt repayments = $400 + $700 + $150 + $600 + $650 = $2,500 DTI = ($2,500 ÷ $6,000) × 100 = 41.7% ```

Still under 50%, but now in the "manageable" range where the rest of the application needs to hold up too.

Add a second credit card, $15,000 limit:

``` Additional obligation = $15,000 × 3.5% = $525 Total debt repayments = $2,500 + $525 = $3,025 DTI = ($3,025 ÷ $6,000) × 100 = 50.4% ```

At 50.4%, DTI crosses the line. The application drops into Possible — lender dependent on this factor alone — regardless of credit score, employment history, or anything else in the profile. Two credit cards this person may rarely touch did that on their own.

What lenders actually look at

• The limit, not the balance, on every card. This is the single biggest reason DTI creeps up unexpectedly. Someone can have a spotless repayment history and still fail on DTI because of unused credit sitting open.
• The new loan is already in the number. Applicants sometimes calculate their "current" DTI and assume that's what gets assessed. It isn't — the repayment on the loan you're asking for is added before the 50% test is applied.
• DTI and affordability are two different checks, and both have to pass. You can sit comfortably under 50% DTI and still fail affordability if your residual income after rent and living costs doesn't cover everything. The reverse is also true — a healthy residual doesn't save you if DTI alone is over 50%. Both are calculated separately, and STRONG requires passing both. See How Much Can I Borrow? for how the affordability side works.
• The display bands matter for how your result reads. Under 35% shows as "Low," 35–49% as "Manageable," and 50%+ as "High — lenders may have concerns." A DTI of 48% and a DTI of 30% both technically pass, but they don't read the same to a lender assessing the rest of your file.

How to improve your DTI

If your DTI is sitting close to or over 50%, these are the levers that actually move it — in rough order of impact.

1. Reduce credit card limits you don't need. Every $1,000 you cut from your total limits removes $35/month from the DTI calculation. This is usually the fastest lever available, because it doesn't require paying down a balance — the limit itself is the number that counts.
2. Close cards you don't use. If a card hasn't been touched in months, closing it removes its limit from the calculation entirely, not just the balance.
3. Pay off or refinance a smaller existing debt. Clearing a car loan or personal loan removes its full monthly repayment from the numerator, not just a portion of it — this tends to have a bigger single-line impact than a partial paydown of anything else.
4. Consider a longer loan term for the loan you're applying for. A longer term lowers the monthly repayment on the new loan, which lowers the number being added into DTI — though it increases the total interest paid over the life of the loan, so weigh that trade-off deliberately.
5. Know that reducing your BNPL repayments helps here too. BNPL is counted at its actual scheduled repayment, so closing accounts you're not using reduces DTI the same way it reduces affordability pressure. See Does BNPL Affect Personal Loan Approval in Australia? for the full picture.

DTI is one number, but it's built from several moving parts — and the credit card line is the one people most often get wrong, because an unused limit still counts as if you could draw on it tomorrow. Add up your actual debt repayments, add 3.5% of every card limit, add the loan you're about to apply for, and divide by your gross monthly income. That's the number a lender sees before anything else about your application gets considered.