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15 Deposit Mortgage Calculator

Reviewed by Calculator Editorial Team

Buying a home with a 15% deposit is a common path for many first-time buyers. This calculator helps you estimate your monthly mortgage payments, total interest paid, and loan amount based on your deposit, property price, interest rate, and loan term.

How the 15% Deposit Mortgage Calculator Works

A 15% deposit mortgage means you put down 15% of the property's purchase price as a down payment. The remaining 85% is financed through a mortgage loan. The calculator uses the standard mortgage payment formula to determine your monthly payments.

Key points about a 15% deposit mortgage:

  • Lower deposit than 20% or 25% options
  • May require mortgage insurance (PMI)
  • Often requires higher interest rates than larger deposits
  • Good for first-time buyers with limited savings

Using a 15% deposit can be beneficial if you want to enter the property market with less upfront capital. However, you'll typically need to pay mortgage insurance and may face higher interest rates compared to larger deposits.

How to Use the Calculator

To use the 15% deposit mortgage calculator:

  1. Enter the property price in your local currency
  2. Select your desired loan term (typically 15-30 years)
  3. Enter your expected annual interest rate
  4. Click "Calculate" to see your results
  5. Review the monthly payment, total interest, and loan amount
Monthly Payment = P * (r(1+r)^n) / ((1+r)^n - 1) Where: P = Principal loan amount r = Monthly interest rate (annual rate / 12) n = Number of payments (loan term in years × 12)

The calculator will show you the monthly payment amount, total interest paid over the loan term, and the actual loan amount (property price minus 15% deposit).

The Mortgage Calculation Formula

The standard mortgage payment formula used by this calculator 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 = Number of payments (loan term in years × 12)

This formula accounts for the amortization of the loan over time, showing how interest is paid down each month while the principal balance decreases.

Variable Description
M Monthly payment amount
P Principal loan amount (property price - 15% deposit)
r Monthly interest rate (annual rate divided by 12)
n Number of monthly payments (loan term × 12)

Worked Example

Let's calculate a mortgage with these assumptions:

  • Property price: $300,000
  • Deposit: 15% ($45,000)
  • Loan amount: $255,000
  • Interest rate: 5% per year
  • Loan term: 25 years
Monthly interest rate = 5% / 12 = 0.4167% (0.004167) Number of payments = 25 × 12 = 300 M = 255,000 [ 0.004167(1+0.004167)^300 ] / [ (1+0.004167)^300 - 1 ] M ≈ $1,428.50 per month

In this example, with a $300,000 property price and 15% deposit, your monthly mortgage payment would be approximately $1,428.50 over 25 years. The total interest paid would be about $123,900, and the total amount repaid would be $378,900.

Frequently Asked Questions

What is a 15% deposit mortgage?
A 15% deposit mortgage means you put down 15% of the property's purchase price as a down payment, financing the remaining 85% through a mortgage loan.
Do I need mortgage insurance with a 15% deposit?
Yes, most lenders require mortgage insurance (PMI) for loans with less than 20% deposit. This protects the lender if you default on the loan.
How does a 15% deposit compare to other options?
A 15% deposit typically results in higher monthly payments and more total interest paid compared to larger deposits like 20% or 25%. However, it may be more affordable than renting.
What factors affect my mortgage payment?
Your monthly payment depends on the loan amount, interest rate, and loan term. A higher interest rate or longer term will increase your monthly payment.