Monthly Loan Payment Calculator
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Monthly Loan Payment Calculator
Your Estimated Monthly Payment
$0.00
Enter loan details to see your estimate.
Understanding Your Monthly Loan Payment
When you take out a loan, whether it's for a car, a home, personal expenses, or business ventures,
the most critical figure to understand is your monthly payment. This is the fixed amount you'll
pay back to the lender each month until the loan is fully repaid. Accurately calculating this
payment is essential for budgeting and financial planning.
Our calculator simplifies this process, providing an instant estimate based on three key factors:
the total loan amount, the annual interest rate, and the loan term.
The Math Behind the Calculation
The calculation for a fixed-rate loan's monthly payment uses a standard amortization formula.
The formula ensures that each payment covers both a portion of the principal amount borrowed
and the interest accrued over the month.
The formula is as follows:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
Where:
- M = Your total monthly mortgage payment.
- P = The principal loan amount (the amount you borrow).
- i = Your monthly interest rate. This is calculated by dividing the annual interest rate by 12 (e.g., 5.5% annual rate becomes 0.055 / 12 = 0.004583).
- n = The total number of payments over the loan's lifetime. This is calculated by multiplying the number of years the loan term by 12 (e.g., a 5-year loan has 5 * 12 = 60 payments).
Our calculator takes your inputs for Loan Amount (P), Annual Interest Rate, and Loan Term (in years)
and applies this formula precisely to give you an estimated monthly payment (M).
Key Inputs Explained:
- Loan Amount: This is the total sum of money you are borrowing from the lender.
- Annual Interest Rate: This is the yearly percentage charged by the lender for borrowing the money. It's crucial to input this as a percentage (e.g., 5.5 for 5.5%). The calculator converts it to a monthly decimal rate.
- Loan Term (Years): This is the total duration over which you agree to repay the loan. A longer term generally means lower monthly payments but more interest paid overall.
Why Use This Calculator?
- Budgeting: Easily estimate how much a potential loan will cost you each month to fit into your budget.
- Comparison Shopping: Compare loan offers from different lenders by inputting their terms to see how the monthly payments vary.
- Financial Planning: Understand the impact of interest rates and loan durations on your long-term financial obligations.
- Decision Making: Make informed decisions about whether a loan is affordable and suitable for your financial situation.
Remember, this calculator provides an estimate for the principal and interest portion of your loan payment.
Depending on the loan type (e.g., mortgage), your actual total monthly payment might also include
escrow for property taxes, homeowner's insurance, and private mortgage insurance (PMI).
function calculateMonthlyPayment() {
var loanAmountInput = document.getElementById("loanAmount");
var annualInterestRateInput = document.getElementById("annualInterestRate");
var loanTermYearsInput = document.getElementById("loanTermYears");
var monthlyPaymentResultDiv = document.getElementById("monthlyPaymentResult");
var loanAmount = parseFloat(loanAmountInput.value);
var annualInterestRate = parseFloat(annualInterestRateInput.value);
var loanTermYears = parseFloat(loanTermYearsInput.value);
// Input validation
if (isNaN(loanAmount) || loanAmount <= 0) {
monthlyPaymentResultDiv.innerHTML = "$0.00
Please enter a valid loan amount.";
return;
}
if (isNaN(annualInterestRate) || annualInterestRate < 0) {
monthlyPaymentResultDiv.innerHTML = "$0.00
Please enter a valid annual interest rate.";
return;
}
if (isNaN(loanTermYears) || loanTermYears <= 0) {
monthlyPaymentResultDiv.innerHTML = "$0.00
Please enter a valid loan term in years.";
return;
}
// Convert annual interest rate to monthly interest rate
var monthlyInterestRate = annualInterestRate / 100 / 12;
// Calculate the total number of payments
var numberOfPayments = loanTermYears * 12;
var monthlyPayment;
// Handle the edge case where the interest rate is 0%
if (monthlyInterestRate === 0) {
monthlyPayment = loanAmount / numberOfPayments;
} else {
// Calculate monthly payment using the amortization formula
var factor = Math.pow(1 + monthlyInterestRate, numberOfPayments);
monthlyPayment = loanAmount * (monthlyInterestRate * factor) / (factor – 1);
}
// Format the result to two decimal places
var formattedMonthlyPayment = monthlyPayment.toFixed(2);
monthlyPaymentResultDiv.innerHTML = "$" + formattedMonthlyPayment + "
Based on your inputs.";
}