Mortgage Amortization Calculator

About the Mortgage Amortization Calculator

A mortgage amortization calculator generates the complete month-by-month schedule showing exactly how every payment over the life of your mortgage is split between interest and principal, and the remaining balance after each payment. Amortization — from the Latin for killing off debt — describes how fixed monthly payments gradually shift from being mostly interest in the early years to mostly principal in the later years, until the loan balance reaches zero. The amortization schedule is not just a mathematical curiosity: it reveals surprising truths about homeownership that most buyers do not know. You do not reach 50% equity (50% of balance paid down) until approximately year 18-20 of a 30-year mortgage. In the first payment on a $300,000 mortgage at 7%, only $246 goes to reducing the principal — $1,750 is pure interest. Our free mortgage amortization calculator generates the full schedule, highlights the year-by-year totals, identifies key milestones (like when you reach 20% and 50% equity), and shows the total interest you will pay over the loan's full life. It is an essential planning tool for any homeowner considering extra payments, refinancing, or simply understanding where their mortgage payments go.

How It Works

Amortization formula: Monthly payment M = P × [r(1+r)^n] / [(1+r)^n - 1]. For each payment month: Interest paid = Current balance × monthly rate r. Principal paid = Monthly payment M - Interest paid. New balance = Prior balance - Principal paid. This repeats for all n months. Example: $320,000 loan, 7% annual rate, 30-year term. Monthly r = 7% / 12 = 0.5833%. n = 360 months. Monthly payment = $320,000 × [0.005833 × (1.005833)^360] / [(1.005833)^360 - 1] = $2,129. Month 1: Interest = $320,000 × 0.005833 = $1,867. Principal = $2,129 - $1,867 = $262. Balance = $319,738. Month 12: Balance ≈ $317,900. Year 1 total principal paid: approximately $3,200 on $320,000 — only 1% of balance in the first year. Year 20: balance ≈ $224,000. Only $96,000 of the $320,000 principal paid after 20 years — 67% of the term elapsed but only 30% of principal retired. Total interest over 30 years: $2,129 × 360 - $320,000 = $446,440.

Tips & Best Practices

• ✓The amortization schedule is the most powerful argument for extra mortgage payments: in year 1, $262 of a $2,129 payment reduces principal. An extra $262/month doubles the principal reduction — a $262 extra payment saves approximately $1,867 in future interest on that same $262.
• ✓Refinancing decision: compare the amortization schedule of your current loan against a refinance. A 30-year refi resets the amortization clock — years of built-up principal paydown are replaced by a new front-loaded interest schedule. This is why refinancing repeatedly at similar rates can cost more total interest than keeping the original loan.
• ✓The 20% equity milestone matters: private mortgage insurance (PMI) on conventional loans cancels when you reach 80% LTV (20% equity). The amortization schedule shows exactly which month this occurs — and whether it is worth making extra payments to reach it sooner.
• ✓Bi-weekly payment strategy: making half your monthly payment every two weeks results in 26 half-payments (13 full payments) per year instead of 12. On a 30-year mortgage, this alone shortens payoff by approximately 4-5 years and saves substantial interest — visible in the amortization schedule.
• ✓Interest deduction planning: mortgage interest is deductible for itemizers. The amortization schedule shows exactly how much interest you paid in any given tax year — this figure goes on Schedule A of your tax return. The schedule also shows interest declining year over year, meaning the tax benefit gradually decreases.
• ✓Comparing 15-year versus 30-year: run both in the amortization calculator. A 15-year mortgage typically carries a 0.5-0.75% lower rate and pays off in half the time. On a $300,000 loan, the total interest difference is often $150,000-$200,000 — one of the biggest financial decisions in homeownership.

Who Uses This Calculator

New homebuyers understanding where their monthly payments go and the true total cost of their mortgage. Homeowners planning extra payments and wanting to see the exact months saved and interest reduced. Anyone evaluating refinancing who needs to compare the remaining amortization schedule of their current loan against a new one. Tax filers needing the exact mortgage interest paid in a given year for Schedule A deduction purposes. Financial educators teaching the mechanics of loan amortization and the time value of money.