Loan Calculator

A loan is a financial arrangement in which a lender provides a specific amount of money to a borrower under the condition that the borrower will repay the loan amount with interest over a predetermined period. Loans are widely used by individuals and businesses to finance various needs, such as buying a home, starting a business, or covering unexpected expenses. This comprehensive guide will explain what a loan is, the different types of loans, and how to calculate various aspects of a loan.

What Is a Loan?

A loan is a financial transaction that involves a lender and a borrower. The lender, often a financial institution like a bank or credit union, provides funds to the borrower for a specified purpose. The borrower agrees to repay the borrowed amount, usually in installments, over a defined period. The lender typically charges interest on the loan, which is the cost of borrowing and the primary source of profit for the lender.

Key Loan Terms

Before we dive into loan calculations, let's familiarize ourselves with some fundamental loan terms:

  • Principal: The initial amount borrowed from the lender.
  • Interest Rate: The cost of borrowing, typically expressed as an annual percentage.
  • Loan Term: The duration over which the borrower agrees to repay the loan.
  • Monthly Payment: The regular payment made by the borrower, consisting of both principal and interest.
  • Amortization: The process of reducing the loan balance through scheduled payments.

Loan Calculation

Monthly Payment Calculation

One of the most critical aspects of loan calculation is determining the monthly payment. The formula for calculating the monthly payment for a fixed-rate loan is:

Monthly Payment (M) = P [r(1 + r)^n] / [(1 + r)^n - 1]


  • M is the monthly payment
  • P is the principal loan amount
  • r is the monthly interest rate (annual rate divided by 12)
  • n is the number of monthly payments (loan term in years multiplied by 12)

Example Calculation

Let's calculate the monthly payment for a loan of $20,000 with a 5% annual interest rate and a 3-year loan term:

M = $20,000 * [0.05/12 * (1 + 0.05/12)^(312)] / [(1 + 0.05/12)^(312) - 1]

M ≈ $601.03

The monthly payment for this loan would be approximately $601.03.

Total Payment and Interest

Over the life of the loan, you'll also want to know the total amount paid and the total interest paid. These can be calculated as follows:

Total Payment = M * n

Total Interest = Total Payment - P

For our example:

Total Payment ≈ $601.03 * 3 * 12 ≈ $21,643.08

Total Interest ≈ $21,643.08 - $20,000 ≈ $1,643.08