How much can you borrow before a new payment squeezes your budget? Many lenders answer that question with your debt-to-income ratio, or DTI. The Loan Affordability Calculator uses a 36% DTI limit to estimate the largest loan your income can support.
You enter your monthly gross income, current debt payments, interest rate, and loan term. The tool shows the highest payment under the 36% limit and the loan it could cover. It suits anyone planning a personal loan, car loan, or other fixed-rate installment loan.
Table of Contents
- What the Calculator Does
- How to Use It, Step by Step
- The Loan Affordability Formula
- Worked Example
- How to Read the Results
- What Changes Your Maximum Loan
- Limitations and Assumptions
- FAQs About the Loan Affordability Calculator
What the Calculator Does
The tool works backward from your income to a loan amount. It runs once when the page loads and again each time you press the button.
- Four inputs: monthly gross income, monthly debt payments, interest rate, and loan term in years.
- Max Affordable Loan: the loan size your spare payment room could repay over the term.
- Max Monthly Payment (36% DTI): 36% of your income minus the debts you already pay.
- Total Debt Ratio (DTI): your own current ratio next to the cap, such as "7.8% Now (36% Cap)."
- Calculate Maximum Loan button to refresh the results after you change any field.
How to Use It, Step by Step
- Type your pay before taxes in Monthly Gross Income ($), at least $500. Include steady income you could show a lender.
- Enter the total of your current minimum payments in Monthly Debt Payments ($). Type 0 if you have none.
- Enter the yearly rate you expect in Interest Rate (%), from 0% to 30%.
- Enter the repayment length in Loan Term (Years), from 1 to 30. Partial years also work.
- Press Calculate Maximum Loan or the Enter key. The cards do not update as you type.
For monthly debts, count car loans, student loans, credit card minimums, and housing payments. Leave out bills like groceries, phone, and utilities, since DTI only counts debt.
The Loan Affordability Formula
The calculator takes two steps. First it finds your payment room, then it turns that payment into a loan amount.
Income × 36%-Current Debts=Max Payment→Max Loan
- Max payment = income × 0.36 - monthly debts. If debts reach 36% of income or more, it becomes $0.
- Current DTI = monthly debts ÷ income × 100, shown with one decimal.
- Max loan = payment × ((1 + r)^n - 1) ÷ (r × (1 + r)^n).
- r is the monthly rate, the yearly rate ÷ 100 ÷ 12.
- n is the number of monthly payments, the term in years × 12.
- At a 0% rate, max loan = payment × n.
This is the standard present value formula for a fixed loan. It assumes equal monthly payments that fully repay the loan by the end of the term.
Worked Example
Andre earns $5,800 a month before taxes. He pays $450 a month on a student loan. He wants to know how big a 5-year loan at 7.5% he could take on.
| Step | Calculation | Result |
|---|
| 36% of income | $5,800 × 0.36 | $2,088.00 |
| Max Monthly Payment | $2,088 - $450 | $1,638.00 |
| Monthly rate and payments | 7.5% ÷ 12, 5 × 12 | 0.625%, 60 payments |
| Max Affordable Loan | Present value of $1,638 for 60 months | $81,744.89 |
| Total Debt Ratio (DTI) | $450 ÷ $5,800 × 100 | 7.8% Now (36% Cap) |
If Andre stretched the term to 6 years, his maximum would rise to $94,736.23. At 8.5% over 5 years, it would fall to $79,838.06.
How to Read the Results
Max Affordable Loan is a ceiling, not a target. Borrowing that much would use every dollar of room under the 36% limit.
Max Monthly Payment (36% DTI) is the new payment that keeps total debt at 36% of gross income. Compare it with real loan quotes before you apply.
Total Debt Ratio (DTI) shows your ratio today, before any new loan. The gap between it and 36% is your room to borrow.
If a field is blank or out of range, a red message names the problem. All three cards then show N/A instead of old numbers.
What Changes Your Maximum Loan
Income and existing debts set your payment room. Paying off a card or car loan frees room right away. Our debt payoff planner can show how fast you could clear those balances.
The rate and term then decide how much loan that payment can carry. A longer term raises the maximum, but you pay more interest overall. Try terms side by side with the loan term calculator.
The 36% figure is a common rule of thumb, not a legal limit. Lenders set their own DTI caps by loan type and credit profile. With a real quote in hand, check it with the personal loan payment calculator or the auto loan calculator.
Gross income also overstates what you can spend, since taxes and daily costs come out first. A monthly budget planner helps confirm the payment fits your take-home pay. More tools live in the finance and business calculator hub.
Limitations and Assumptions
- The 36% limit is fixed. You cannot change it to match a lender that uses a different cap.
- The tool ignores fees, insurance, taxes, and down payments. It assumes a fixed rate and equal payments.
- Results change only when you press the button. Edited fields can sit next to old results.
- Income must be at least $500, the rate 0% to 30%, and the term 1 to 30 years.
- It does not check your credit score, job history, or collateral, which lenders also weigh.
FAQs About the Loan Affordability Calculator
What is a debt-to-income ratio?
It is your total monthly debt payments divided by your monthly gross income. Lenders use it to judge whether you can handle another payment.
Why does the calculator use 36%?
Many lenders and planners treat 36% total DTI as a comfortable upper range. It is a rule of thumb, and real lender limits can be higher or lower.
Why does my maximum loan show $0.00?
Your current debts already equal or exceed 36% of your income. For example, $4,000 income with $1,500 in debts gives "37.5% Now (36% Cap)." Both money cards read $0.00, and a note explains why.
Should I use gross or take-home income?
Use gross income, since DTI rules are based on pay before taxes. Then check the payment against your take-home pay to make sure it truly fits.
Does a longer loan term help me borrow more?
Yes, a longer term spreads the same payment over more months, so the maximum rises. You will also pay more total interest over the life of the loan.
Can I use this for a mortgage?
You can get a rough idea, but the tool skips property taxes, insurance, and down payments. A dedicated mortgage tool gives a fuller picture for home loans.
This calculator gives planning estimates only and is not financial advice. Reviewed for general accuracy by Prof. Dr. Khalil Mudassar, PhD.