How to Use This Calculator
- 1
Enter Your Monthly Income
Input your total gross income per month before any taxes or deductions.
- 2
List Monthly Debt Payments
Provide the total amount you currently pay each month towards existing debts like credit cards, car loans, or student loans.
- 3
Specify Desired Loan Amount
Enter the principal amount you wish to borrow.
- 4
Enter Annual Interest Rate
Input the annual interest rate (APR) for the new loan as a percentage.
- 5
Set the Loan Term
Enter the repayment period in months.
- 6
Set Maximum Affordable Payment
Enter the maximum amount you can realistically afford to pay each month.
- 7
Review Your Results
The calculator displays your Monthly Payment, Total Interest, Total Amount Paid, and Debt-to-Income Ratio. The insights panel shows whether the loan fits your budget and how much income remains after debt.
Example Calculation
A prospective car buyer wants to determine the monthly payment for a $20,000 vehicle loan and check if it fits their budget.
Monthly Income
$4,000
Monthly Debt Payments
$500
Desired Loan Amount
$20,000
Annual Interest Rate
6%
Loan Term
60 months
Maximum Affordable Payment
$400
Results
Monthly Payment
$386.66
Total Interest
$3,199.36
Total Amount Paid
$23,199.36
Debt-to-Income Ratio
22.2%
Insights card shows affordability analysis with budget comparison, remaining income, and true borrowing cost.
Tips
Prioritize High-Interest Debt First
If your existing monthly debt payments are high, consider tackling debts with 20%+ APR before taking on a new loan. Reducing a $500 credit card minimum could significantly improve your DTI ratio.
Build a Payment Buffer
Aim for a monthly payment comfortably below your maximum. A 10-15% buffer protects against unexpected expenses — on a $386.66 payment, that means keeping your max at $430 or higher.
Check Your DTI Before Applying
Most lenders prefer a total debt-to-income ratio below 36%. Use this calculator to confirm your DTI stays in range before applying, as a higher ratio may mean worse terms or denial.
Understanding Loan Affordability
Taking on a loan is a significant financial commitment.
The Loan Affordability Calculator helps you determine whether a specific loan fits within your budget by calculating the monthly payment and comparing it against your income, existing debts, and maximum affordable threshold.
For instance, a $20,000 loan at 6% over 60 months requires a monthly payment of $386.66, which — combined with $500 in existing debt on $4,000 income — produces a debt-to-income ratio of 22.2%.
The Monthly Payment Formula
The calculator uses the standard amortization formula to determine your monthly payment:
Monthly Payment = (Loan Amount x Monthly Rate) / (1 - (1 + Monthly Rate)^-Term)
Where:
Loan Amountis the principal sum borrowedMonthly Rateis the annual interest rate divided by 12 (e.g., 6% / 12 = 0.5% or 0.005)Termis the total number of monthly payments
Additional calculations:
Total Interest = (Monthly Payment x Term) - Loan Amount
Debt-to-Income Ratio = (Existing Debt + Monthly Payment) / Monthly Income x 100%
Worked Example: Car Loan Affordability
Consider a buyer earning $4,000/month with $500 in existing debt payments, considering a $20,000 car loan at 6% for 60 months, with a self-imposed maximum of $400/month.
- Monthly interest rate: 6% / 12 = 0.5% (0.005)
- Monthly payment: ($20,000 x 0.005) / (1 - (1.005)^-60) = $100 / 0.258628 = $386.66
- Total interest: ($386.66 x 60) - $20,000 = $3,199.36
- Total amount paid: $386.66 x 60 = $23,199.36
- DTI ratio: ($500 + $386.66) / $4,000 = 22.2%
The payment of $386.66 is below the $400 maximum, and the 22.2% DTI is well under the 36% guideline — this loan is affordable.
The 28/36 Rule for Loan Affordability
Financial advisors commonly reference the 28/36 rule: keep housing-related debt below 28% of gross income, and total debt below 36%.
For a $4,000/month earner, that means total debt payments should stay under $1,440/month.
With $500 in existing debt and a $386.66 loan payment, total debt is $886.66 — only 22.2% of income, well within the guideline and leaving $553/month of capacity before hitting 36%.
When to Reconsider a Loan
If the calculator shows your payment exceeds your maximum affordable amount or your DTI rises above 36%, consider these adjustments:
- Reduce the loan amount — borrowing $15,000 instead of $20,000 at the same terms drops the payment to $289.99/month
- Extend the term — stretching to 72 months lowers the payment but increases total interest
- Shop for a lower rate — even 1% lower (5% vs. 6%) saves $554 in total interest on a $20,000/60-month loan
- Pay down existing debt first — reducing your $500 existing payment improves both DTI and remaining income
Frequently Asked Questions
What does loan affordability mean?
Loan affordability refers to your capacity to comfortably manage new loan payments without compromising existing financial obligations. It considers your income, current debts, the proposed loan amount, and interest rate — typically assessed through the debt-to-income (DTI) ratio, which compares total monthly debt to gross income.
How do lenders determine loan affordability?
Lenders primarily use the debt-to-income (DTI) ratio, comparing total monthly debt payments to gross monthly income. Most prefer a DTI below 36% for favorable terms, while ratios above 43% often trigger higher scrutiny or denial, per CFPB guidelines.
What is a good monthly payment for a loan?
A good monthly payment keeps your total DTI ratio below 36%, including the new loan. It should leave enough income for savings, emergencies, and daily expenses. For example, on $4,000/month income with $500 in existing debt, a $386.66 loan payment brings DTI to 22.2% — well within guidelines.
Does a longer loan term make a loan more affordable?
A longer term lowers your monthly payment but increases total interest. For example, a $20,000 loan at 6% costs $386.66/month over 60 months ($3,199 interest) vs. $222.04/month over 120 months ($6,645 interest). The monthly payment drops 43% but total interest more than doubles.