Debt to Income Calculator

About the Debt to Income Calculator

DTI is the ratio lenders use to decide whether you can afford to borrow, and it has one feature that makes it consistently misleading to the person being measured:

It is calculated on gross income.

A 36% DTI sounds like roughly a third of your money. It is 36% of income you never actually receive. Once tax and deductions come out, the same commitments are a substantially larger share of what arrives in your account — and that larger figure is the one you live on.

This debt to income calculator reports both: the ratio a lender computes, and the ratio your bank balance experiences.

How to Use the Debt to Income Calculator

Enter your gross monthly income — before tax, because that is what lenders use.

Take-home pay is optional and is the more revealing of the two. Leave it at zero to skip that comparison.

Housing cost is rent or mortgage, plus property tax and insurance where those are billed separately. Other debt payments covers car loans, student loans, card minimums — anything with a required monthly payment.

The two limits are lender policy rather than arithmetic, which is why they are inputs. They vary by product, by lender and by country.

Step-by-Step Example

£6,000 gross, £4,400 take-home, £1,500 housing, £600 other debt.

  Front-end:  1,500 ÷ 6,000          =  25%
  Back-end:  (1,500 + 600) ÷ 6,000   =  35%

Both inside the usual 28% and 36% guides. A lender would look at this and see a comfortable application.

Now the same commitments against what actually arrives:

  2,100 ÷ 4,400  =  47.73%

Not 35%. Nearly 48% — and £2,300 a month left for food, energy, transport, childcare, savings and everything else.

The gap is 12.73 percentage points, and it is entirely tax and deductions. A ratio that passes a lender's test comfortably can be a tight budget in practice, and nothing in the lender's figure tells you that.

Front-End and Back-End

Both get called DTI and they are not interchangeable.

Front-end is housing costs alone against income. The common guide is under 28%.

Back-end adds every other debt payment. The common guide is under 36%, though plenty of lending goes higher for a strong application.

Which one is quoted at you depends on who is quoting. When a mortgage broker says "your DTI is fine", it is worth asking which one they mean.

Which Limit Is Actually Stopping You

This is the most actionable output, and it is often not what people expect.

  Front-end limit allows:  28% of 6,000            =  1,680
  Back-end limit allows:   36% of 6,000 − 600      =  1,560
                                                      ─────
  Binding constraint:      the back end, at 1,560

The housing limit would allow £1,680. The other debts pull it down to £1,560.

Which means the fastest way to afford more housing is not to earn more or save a bigger deposit — it is to clear a debt. A required monthly payment counts in full against the ratio regardless of how small the balance behind it is.

Clearing a £600-a-month car loan frees the whole £600 against this ratio immediately. That is why a modest balance cleared before a mortgage application often moves the answer further than months of extra saving would.

What DTI Does Not Include

Worth knowing in both directions.

It counts required debt payments only. It does not count groceries, energy, childcare, transport, insurance, pension contributions or savings.

So a ratio inside the limits does not mean the budget works. It means the lender's test passes. Those are different claims, and the second one is the one being made.

Check what is left over after everything, not just the percentage.

Understanding Your Result

Your ratios gives front-end and back-end together.

Against the limits says whether each clears, and names the one that does not.

On take-home pay is the ratio you actually live with, plus what is left each month.

What you could support shows the housing cost these limits allow and how far you are from it.

Worth knowing points at the lever — usually other debt rather than housing.

When Should You Use This Calculator?

Before a mortgage application. Particularly to see whether other debt is what is limiting you.

When deciding whether to clear a loan early. It frees its whole payment against the ratio at once.

When comparing what a lender says you can afford against what you can afford. These are routinely different numbers.

After a change in income. A pay rise moves the gross ratio more than it moves the take-home one.

Common Mistakes

Reading a gross ratio as a share of your money. It is a share of income you do not receive.

Confusing front-end with back-end. They differ by every non-housing debt you have.

Treating the limits as fixed rules. They are lender policy and vary considerably.

Assuming a passing ratio means an affordable budget. DTI ignores every living cost you have.

Paying down a large balance instead of clearing a small one. For this ratio, the monthly payment is what counts, not the balance — so clearing the smallest loan outright often helps more than reducing the largest.

Forgetting that new debt counts immediately. A car finance agreement signed the month before a mortgage application changes the answer.

Every figure here is an estimate for planning. Lending criteria vary considerably and this is not financial advice.