Loan Calculator: How to Calculate Monthly Payments, Total Interest, and Affordability for Any Loan

Before signing any loan agreement, knowing exactly what your monthly payments will be and how much interest you will pay over the full term is essential. Even a small difference in interest rates can mean thousands of dollars over the life of a loan. Use the free Loan Calculator to run the numbers before you commit.

What Goes Into a Loan Payment?

Every loan payment consists of two parts:

  • Principal: The original amount you borrowed
  • Interest: The cost of borrowing, calculated as a percentage of the remaining balance

In the early years of a loan, most of your payment goes toward interest. As the balance decreases, more of your payment goes toward principal — this is called amortization.

How to Calculate Monthly Loan Payments

The standard formula for calculating a fixed-rate loan payment is:

M = P × [r(1+r)^n] / [(1+r)^n – 1]

Where:

  • M = Monthly payment
  • P = Principal loan amount
  • r = Monthly interest rate (annual rate ÷ 12)
  • n = Total number of payments (loan term in years × 12)

Loan Payment Examples by Amount and Term

Loan AmountInterest RateTermMonthly PaymentTotal InterestTotal Cost
$10,0006%3 years$304.22$951.88$10,951.88
$10,0006%5 years$193.33$1,599.68$11,599.68
$25,0007%5 years$495.03$4,701.64$29,701.64
$25,0007%7 years$376.75$6,646.69$31,646.69
$50,0008%10 years$606.64$22,796.38$72,796.38

Key insight: A longer term means lower monthly payments but significantly more interest paid over the life of the loan. Use the Loan Calculator to compare different term lengths side by side.

How Interest Rate Affects Your Loan Cost

Even a 1% difference in interest rate can save or cost you thousands. Here is how a $30,000 auto loan at different rates compares over a 5-year term:

Interest RateMonthly PaymentTotal Interest Paid
4%$552.50$3,149.70
5%$566.14$3,968.08
6%$579.98$4,798.97
7%$594.04$5,642.15
8%$608.29$6,497.41

How Much Loan Can You Afford?

A common rule of thumb is the 28/36 rule: your total monthly debt payments should not exceed 36% of your gross monthly income, and your housing costs should not exceed 28%. For a loan calculator perspective:

  • Calculate your monthly take-home pay
  • Subtract existing monthly debts (credit cards, student loans, car payments)
  • The remainder is what you can reasonably put toward the new loan payment

For example, if you earn $5,000/month and have $800 in existing debts, you have approximately $1,000 available for a new loan payment (36% of $5,000 = $1,800, minus $800).

Types of Loans and Typical Rates (2026)

Loan TypeTypical APR RangeTypical Term
Auto Loan (new)5-9%3-7 years
Auto Loan (used)7-14%3-6 years
Personal Loan7-36%1-7 years
Mortgage (30-year fixed)6-8%15-30 years
Student Loan (federal)5-8%10-25 years
Credit Card18-28%Revolving

Before taking out any loan, run the numbers through the free Loan Calculator at Today Calculator to understand your true cost.

Leave a Reply