Question 1

How is a monthly mortgage payment calculated?

Accepted Answer

The monthly mortgage payment is calculated using the amortization formula: M = P[r(1+r)^n] / [(1+r)^n - 1]. P is the loan principal (home price minus down payment), r is the monthly interest rate (annual rate / 12 / 100), and n is the total number of monthly payments (years times 12). This formula ensures equal monthly payments over the full loan term, with the proportion going to interest decreasing over time as the principal balance is paid down.

Question 2

What is the difference between a 15-year and 30-year mortgage?

Accepted Answer

A 15-year mortgage has higher monthly payments but a significantly lower total interest cost. A 30-year mortgage spreads payments over a longer period, resulting in lower monthly payments but much more interest paid over the life of the loan. For example, a $240,000 loan at 6.5% costs about $1,517/month over 30 years (total interest ~$306,000) versus $2,091/month over 15 years (total interest ~$136,000).

Question 3

How much down payment do I need for a mortgage?

Accepted Answer

Conventional mortgages typically require 3-20% down. FHA loans require as little as 3.5% down. VA and USDA loans may allow 0% down for eligible borrowers. Putting down at least 20% eliminates the requirement for private mortgage insurance (PMI), which can add $50-$200+ per month to your payment. A larger down payment also means a smaller loan, lower monthly payments, and less total interest paid.

Question 4

Does this calculator include taxes and insurance?

Accepted Answer

This calculator computes principal and interest (P&I) only. Your actual monthly housing cost will also include property taxes, homeowners insurance, and possibly PMI or HOA fees. As a rough estimate, property taxes and insurance typically add 1-3% of the home value per year. You can expect your total monthly cost to be 20-40% higher than the P&I amount shown.

Question 5

How does interest rate affect total mortgage cost?

Accepted Answer

Interest rate has an enormous impact on the total cost of a mortgage. On a $300,000 30-year loan, each 0.5% increase in the rate adds roughly $30,000-$35,000 to the total interest paid over the life of the loan. This is why even small improvements in your interest rate, such as through buying discount points or improving your credit score, can lead to substantial long-term savings.

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