What is a mortgage calculator?
A mortgage calculator helps you estimate your monthly home loan payment and understand the full cost of your mortgage. Unlike a generic loan calculator where you enter the loan amount directly, this mortgage calculator takes home price and down payment percentage as inputs — just like the real home-buying process. For other types of borrowing, use the Loan Payment Calculator instead.
How is a mortgage payment calculated?
The monthly mortgage payment is calculated using the annuity formula: M = P × r × (1+r)ⁿ / ((1+r)ⁿ − 1), where P is the loan amount (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 × 12).
What is a mortgage amortization schedule?
A mortgage amortization schedule is a table showing every payment across the full loan term, with each payment split into the portion that pays interest and the portion that reduces the principal (loan balance). Early payments are heavily weighted toward interest — on a $240,000 loan at 4% for 30 years, the first payment of $1,146 includes $800 of interest and only $346 of principal reduction. By the final years the split reverses. The schedule reveals the true borrowing cost: over 30 years on that same loan you pay $172,000 in interest — on top of the original $240,000.
What are some mortgage calculation examples?
Example 1: $400,000 home, 20% down, 3.5% rate, 30 years → loan $320,000, monthly payment $1,437.60, total interest $197,536.
Example 2: $250,000 home, 10% down, 5% rate, 25 years → loan $225,000, monthly payment $1,315.91, total interest $169,773.
When should I use a mortgage calculator?
Use this mortgage calculator when comparing mortgage offers, deciding between 15-year and 30-year terms, evaluating the impact of a larger down payment, or planning when to make extra payments to reduce your total interest. Switching from a 30-year to a 15-year term can save tens of thousands in interest. To model how extra payments build toward a financial milestone, the FIRE calculator shows how home equity and investment growth work together on the path to financial independence.
How does the down payment affect the mortgage?
A larger down payment reduces the loan amount directly, lowering both the monthly payment and total interest. Down payments below 20% often require private mortgage insurance (PMI), which adds to the monthly cost. On a $300,000 home, increasing the down payment from 10% to 20% saves about $166 per month at 4% for 30 years.
How do extra mortgage payments reduce total interest?
Even modest additional payments have an outsized effect because they reduce the principal balance earlier, eliminating future interest charges on that amount. On the $240,000 example above (4%, 30 years), the standard monthly payment is about $1,146 and total interest ≈ $172,000. Adding just $200 extra per month — total $1,346 — cuts the loan term to around 23 years and saves roughly $48,000 in interest. Extra payments are most effective early in the loan when the outstanding balance is highest and each dollar of extra principal prevents the most future interest.