Amortization Schedule Calculator
Generate a complete month-by-month amortization table showing principal, interest, and remaining balance.
Results
Visualization
How It Works
An amortization schedule calculator breaks down each monthly loan payment into principal and interest components, showing exactly how much of each payment reduces your debt versus goes to interest costs. This tool helps borrowers understand the true cost of their loan and track how their balance decreases over time. This tool is designed for both quick estimates and detailed planning scenarios. Results update instantly as you adjust inputs, making it easy to compare different approaches and understand how each variable affects the outcome. For best accuracy, use precise measurements rather than rough estimates, and consider running multiple scenarios to establish a realistic range of expected results.
The Formula
Variables
- P — Principal — the original loan amount you borrow before any interest is applied
- r — Monthly interest rate — your annual interest rate divided by 12 (and converted to decimal form)
- n — Total number of payments — the loan term in months (years × 12)
- Monthly Payment — The fixed amount you pay each month that includes both principal and interest
- Remaining Balance — The unpaid principal amount after each monthly payment, which decreases throughout the loan term
Worked Example
Let's say you borrow $200,000 for a house at 6% annual interest over 30 years (360 months). First, convert the annual rate to a monthly rate: 6% ÷ 12 = 0.5% or 0.005 in decimal form. Using the amortization formula, your monthly payment is approximately $1,199.10. In month one, your interest charge is $200,000 × 0.005 = $1,000, so $199.10 goes toward principal and your balance drops to $199,800.90. In month two, interest is calculated on $199,800.90, which equals $999, leaving $200.10 for principal. Notice how early payments are mostly interest while later payments chip away more at principal. By month 360, you'll have paid approximately $431,676 in total interest on your $200,000 loan.
Practical Tips
- Make bi-weekly payments instead of monthly to align with paychecks and reduce interest costs — you'll make 26 half-payments per year (equivalent to 13 full payments) rather than 12, accelerating payoff by several years on a 30-year mortgage.
- Use the amortization schedule to identify when you'll reach 80% loan-to-value (LTV) if it's a mortgage, which is when you can potentially drop PMI (private mortgage insurance) and lower your monthly costs.
- Compare different loan terms side-by-side: a 15-year mortgage has a higher monthly payment but costs far less in total interest than a 30-year mortgage, even at the same interest rate.
- If you receive a bonus or tax refund, apply it directly to principal (specify this with your lender) rather than spreading it across regular payments — this creates significant long-term savings on a 20-30 year loan.
- Watch for loans with variable rates that adjust after an initial period; use today's rate to calculate, but plan for payment increases in your budget since your amortization schedule will change when rates adjust.
Frequently Asked Questions
Why do I pay so much more interest at the beginning of my loan?
Interest is calculated on the remaining balance, so when you owe the most money early in the loan, the interest charges are largest. As you pay down principal, the balance shrinks and less of each payment goes to interest. On a 30-year mortgage, you might pay 70% of your total interest in the first 10 years and only 5% in the last 10 years.
What happens to my amortization schedule if I make extra principal payments?
Extra principal payments reduce your remaining balance immediately, which lowers the interest calculated in future months. This shortens your loan term and reduces total interest paid. For example, adding $200/month to a 30-year mortgage can reduce it to approximately 22 years and save over $100,000 in interest.
How is the monthly payment calculated to stay exactly the same each month?
The monthly payment amount is determined using a standard amortization formula that ensures your fixed payment will fully repay the loan over your chosen term. The formula balances the principal and interest so that early payments cover more interest (since the balance is higher) while later payments cover more principal (as the balance shrinks), but the total payment remains constant.
Can I use an amortization calculator for different types of loans?
Yes, this calculator works for any fixed-rate loan including mortgages, auto loans, personal loans, and student loans. It does not work for variable-rate loans where the interest rate changes during the loan term, or for interest-only loans where you don't pay principal upfront. For those loans, you'd need a more specialized calculator.
What's the difference between principal and interest on my tax return?
If you itemize deductions, mortgage interest may be tax-deductible, but principal payments are not (they're simply repayment of borrowed money). The amortization schedule shows you exactly how much is interest versus principal each year, which you can use to calculate tax deductions. However, personal loan and auto loan interest is generally not tax-deductible for individual borrowers.
Sources
- Federal Reserve: Understanding Mortgage Basics
- Consumer Financial Protection Bureau: What is an amortization schedule?
- IRS Publication 936: Home Mortgage Interest Deduction