What Is Loan Amortization?
Loan amortization explained simply — how each payment is split between interest and principal, and why it matters.
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Loan Repayment CalculatorMonthly Payment + Amortization
Calculate your monthly loan payment, total interest paid, and full amortization schedule. Works for mortgages, auto loans, personal loans, and student loans.
Last updated: Reviewed by CalcGrowth Editorial Team
What This Loan Calculator Does
This free loan repayment calculator shows you exactly what a fixed-rate loan will cost — your monthly payment, the total interest you'll pay over the life of the loan, the full payoff timeline, and a month-by-month amortization schedule. Enter the loan amount, the annual interest rate (APR), the term, and (optionally) an extra monthly payment, and the numbers update instantly — no signup, no email, no data leaves your browser.
It's built for anyone weighing a borrowing decision: home buyers comparing 15-year vs 30-year mortgages, car shoppers deciding between 48 and 72-month auto loans, students mapping out repayment, small business owners checking cash flow against a working-capital loan, and existing borrowers who want to see how much faster they could pay off debt with a small extra payment each month.
By the end of this page you'll understand how loan payments are calculated, what each input does, how amortization shifts interest and principal over time, and the most effective strategies to pay off a loan faster and slash total interest. Three real worked examples below show how a few small changes — a slightly shorter term, a lower rate, or $100 extra per month — can save you thousands.
Your Loan
Enter the details to see your monthly payment.
💡 Tip: Adding even a small extra monthly payment can dramatically cut total interest.
Total borrowed
$
The total sum you're borrowing from the lender.
APR %
%
The yearly rate your lender charges on the loan.
Total length
How long you'll take to pay the loan back in full.
Optional
$
Any extra you pay each month to clear the loan faster.
Your monthly payment will be
$0.00
Based on $250,000 at 6.5% APR over 30 years.
Total Interest
$318,862
Total Paid
$568,861
Payoff Time
30 years
Save or share your results
Copy a link with your inputs pre-filled, or share this plan with someone.
What this means
You'll pay $318,862 in interest — over half your loan amount. Adding even a small extra monthly payment could cut this significantly.Result Summary
Monthly Payment
$1,580.17
Total Interest
$318,862
Total Repayment
$568,861
This means you'll pay $318,862 in interest over 30 years — a total of $568,861 repaid on your $250,000 loan.
Recommended next steps
Based on your loan, here's what most people explore next.
Pay off your loan faster
Simple strategies to reduce interest and finish years earlier.
Read the guidePlanning a home loan?
Estimate your full mortgage payment including taxes & insurance.
Open mortgage calculatorSave for the down payment
Work out how much to set aside each month to hit your goal.
Plan your savingsWant to compare? Try a second loan side-by-side — change the rate, term, or extra payment to see exactly how much you'd save.
💡 Try adding a small extra payment each month — even modest overpayments can save thousands in interest and shave years off your loan.
How this calculator works
Enter your loan amount, the annual interest rate (APR), and the loan term (in months or years). Optionally add an extra monthly payment to model paying down the loan faster.
The calculator returns your monthly payment, the total interest you'll pay over the loan, the payoff time, and a complete month-by-month amortization schedule showing how each payment splits between interest and principal.
Example calculation
A $20,000 car loan at 7% for 5 years:
- Monthly payment: about $396
- Total paid over 5 years: about $23,761
- Total interest: about $3,761
- Add $100/month extra → loan paid off ~14 months early, saving ~$900 in interest.
What this means
Your monthly payment is what you'll actually budget for, but the total interest is the real cost of borrowing. A small change in rate or term can shift total interest by thousands. Extra payments work because every extra dollar reduces the balance interest is charged on for every remaining month.
Tips
- Shop at least 3 lenders — rates vary more than people expect.
- Choose the shortest term you can comfortably afford.
- Round up your payment — even an extra $25/month adds up.
- Avoid borrowing more than you need — every $1,000 less is real money saved.
- Watch out for prepayment penalties on some auto and personal loans.
Frequently asked questions
What's the difference between APR and interest rate?
The interest rate is the cost of borrowing the principal. APR includes interest plus most fees, so it's a better measure of the true yearly cost.
Are extra payments always worth it?
Almost always — but check first that your loan has no prepayment penalty and that you've already covered higher-interest debt and an emergency fund.
Will this calculator work for any loan type?
Yes, any fixed-rate installment loan: personal loans, auto loans, student loans, and mortgages all use the same amortization formula.
Why are my early payments mostly interest?
Interest is charged on the remaining balance, which is highest at the start. As the balance shrinks, more of each payment goes to principal.
Does this account for fees or insurance?
No — it's principal and interest only. Add origination fees, insurance, or taxes separately when comparing total cost.
Keep exploring
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How to Calculate Loan Payments
Lenders use a standard amortization formula to calculate fixed monthly payments on installment loans. The formula is:
M = P × r × (1 + r)^n / ((1 + r)^n − 1)- M — monthly payment
- P — loan amount (principal)
- r — monthly interest rate (annual rate ÷ 12)
- n — total number of monthly payments
Example: A $250,000 mortgage at 6.5% APR over 30 years gives a monthly payment of about $1,580. Over the full term you'll pay roughly $319,000 in interest — more than the original loan amount.
What Affects Your Loan Payments
Four main inputs determine your monthly payment and total interest cost:
- Interest rate. Even a 1% difference can mean tens of thousands of dollars over a 30-year mortgage. Shop around and improve your credit score before applying.
- Loan term. Longer terms reduce monthly payments but dramatically increase total interest. A 15-year mortgage costs much less in interest than a 30-year one.
- Principal (loan amount). Borrowing less is always cheaper. A bigger down payment lowers your principal and your monthly payment.
- Extra payments. Paying more than the minimum each month reduces principal faster, slashing total interest and shortening the loan.
Curious about strategies? Read our guide on how to pay off a loan faster, or see how much you should save each month to balance debt payoff with long-term savings.
Amortization Explained
Amortization is how a loan is paid off through equal monthly payments. Each payment is split between interest and principal, but the proportions change every month:
- Early payments are mostly interest because the balance — and therefore the interest charge — is highest at the start.
- Later payments are mostly principal because the balance has shrunk and less interest accrues.
The amortization schedule above shows this breakdown for every single month of your loan. Open it to see exactly how much interest vs principal you pay each month.
How Extra Payments Save Money
Every extra dollar you pay goes directly to principal. That reduces the balance interest is calculated on for every remaining month — so the savings compound.
Example: On a $250,000 mortgage at 6.5% over 30 years, paying just $200 extra per month saves about $95,000 in interest and pays the loan off roughly 7 years early.
Use the "Extra Monthly Payment" field above to model your own scenario — the calculator will show your interest savings instantly.
Three Worked Loan Examples
Here's how the same calculator handles three very different loans. Each example shows the monthly payment, the total interest cost, and how much you'd save by adding a small extra payment each month.
| Loan | Amount | Rate | Term | Monthly | Total Interest |
|---|---|---|---|---|---|
| Personal loan | $10,000 | 10% | 5 yrs | $212 | $2,748 |
| Auto loan | $30,000 | 7% | 6 yrs | $511 | $6,827 |
| Mortgage | $250,000 | 6.5% | 30 yrs | $1,580 | $318,861 |
Example 1 — $10,000 personal loan at 10% for 5 years
The base monthly payment is about $212 and total interest is around $2,748. Add just $50 extra per month and you'd pay the loan off about 13 months early and save roughly $700 in interest — for less than $2 a day.
Example 2 — $30,000 auto loan at 7% for 6 years
The monthly payment is about $511 with around $6,827 in total interest. An extra $100 per month shortens the loan by roughly 14 months and saves close to $1,400 in interest. Choosing 5 years instead of 6 at the same rate would cut interest by another ~$1,200.
Example 3 — $250,000 mortgage at 6.5% for 30 years
The base monthly payment is about $1,580, but you'll pay nearly $319,000 in interest over the life of the loan — more than the original principal. Adding $200 extra per month saves about $95,000 in interest and pays the mortgage off about 7 years early. Plug your own numbers in above to see your version of this scenario.
How Does This Loan Calculator Work?
This free online loan calculator takes four inputs — loan amount, annual interest rate, term, and an optional extra monthly payment — and instantly returns your monthly payment, total interest paid, total cost, and a full month-by-month amortization schedule. It works for any fixed-rate installment loan, including auto loans, personal loans, student loans, and home loans.
Behind the scenes it uses the same amortization formula every bank uses, then simulates each month of the loan to show how your balance, principal, and interest change over time. No data is sent to a server — every calculation runs in your browser.
How to Pay Off a Loan Faster
Whether you're trying to pay off a personal loan, car loan, or mortgage early, the strategy is the same: get more money to principal each month. Here are the most effective ways to pay off a loan faster:
- Make biweekly payments. Paying half your monthly payment every two weeks adds up to one extra full payment per year.
- Round up your payment. Rounding $487 up to $550 sends ~$63 extra to principal every month with no real budget pain.
- Apply windfalls. Tax refunds, bonuses, and cash gifts go a long way when applied as lump-sum principal payments.
- Refinance to a lower rate. If rates have dropped, refinancing can cut years off your loan and reduce total interest dramatically.
- Switch to a shorter term. Moving from a 30-year to a 15-year loan increases the monthly payment but slashes total interest.
Use the extra monthly payment field above to model any of these strategies and see exactly how many months and how much interest you'd save.
How to Calculate Interest on a Personal or Auto Loan
For a fixed-rate loan, monthly interest is simply your current balance × the monthly interest rate (annual rate ÷ 12). Each month, the lender charges interest on whatever you still owe, then applies the rest of your payment to principal. Because the balance shrinks every month, the interest portion shrinks too — which is why later payments wipe out principal much faster than early ones.
To estimate total interest on any loan — auto loan, personal loan, student loan, or small business loan — enter the loan amount, APR, and term above. The total interest figure shows exactly how much the loan will cost you on top of the principal.
How to Use This Loan Calculator With Extra Payments
Five quick steps to get an accurate repayment estimate:
- Enter your loan amount — the principal you plan to borrow.
- Add the interest rate — use APR if you have it.
- Set the loan term — in years or months (auto loans are usually 36–84 months, mortgages 15–30 years).
- Optional: add an extra monthly payment — to see how much faster you can pay it off.
- Review the results — monthly payment, total interest, payoff time, and the full amortization schedule update instantly.
Common Use Cases for the Loan Calculator
- Compare auto loan offers — test 48 vs 60 vs 72-month terms to see total interest at each.
- Pay off a personal loan early — try $50, $100, or $200 extra per month to see months and interest saved.
- Plan student loan repayment — model standard vs accelerated payoff schedules.
- Estimate a small business loan — check if the monthly payment fits inside your projected cash flow.
- Decide between cash vs financing — compare the total cost of borrowing against paying upfront.
Tips to Improve Your Loan Results
- Boost your credit score before applying. Even a 40-point jump can drop your rate by 1%+.
- Get quotes from at least 3 lenders. Banks, credit unions, and online lenders often differ by full percentage points.
- Choose the shortest term you can afford. Total interest drops sharply with shorter terms.
- Avoid prepayment penalties. Confirm you can pay extra without fees before signing.
- Round payments up. Rounding $312 to $350/month is a near-painless way to slash interest.
Frequently Asked Questions
What is APR versus the interest rate?
The interest rate is the pure cost of borrowing the principal. APR (annual percentage rate) includes the interest plus origination fees, discount points, and most other lender charges, expressed as an annualised percentage. APR is the better number for comparing two loan offers, because a loan with a low rate but high fees can easily be more expensive than one with a slightly higher rate and no fees. This calculator uses the interest rate; add fees separately when you want the true APR.
What is the difference between a secured and an unsecured loan?
A secured loan is backed by collateral — a house for a mortgage, a car for an auto loan, or a savings account for a secured personal loan. Because the lender can seize the collateral if you default, rates are lower. An unsecured loan (most personal loans and credit cards) has no collateral, so the lender relies on your credit alone and charges a higher rate. Secured loans typically run 5–8% today, while unsecured personal loans often price at 10–20%+ depending on credit.
How is a loan payment calculated?
Loan payments use the amortization formula M = P × r × (1+r)^n / ((1+r)^n − 1), where P is the principal, r is the monthly interest rate (annual rate ÷ 12), and n is the total number of monthly payments. Each fixed payment covers the interest accrued on the outstanding balance first, and the leftover reduces principal. That's why early payments are mostly interest and later payments are mostly principal.
What is an origination fee and how much does it add to the loan?
An origination fee is a one-time charge (typically 1–8% of the loan) that the lender takes for processing the loan, usually deducted from the amount you receive. On a $20,000 personal loan with a 5% origination fee, you get $19,000 but repay based on $20,000 at the stated rate — which pushes the true APR meaningfully above the interest rate. Always compare offers by APR, not the headline rate, and treat any origination fee above 5% as a red flag.
Are prepayment penalties something to worry about?
For most modern personal, auto, and mortgage loans in the US, no — federal rules restrict prepayment penalties on qualified mortgages and most auto lenders have dropped them. But they still appear on some subprime auto loans, older mortgages, and non-bank personal loans. Always check the loan agreement for a 'prepayment penalty' clause before making extra payments or refinancing; if one exists, run the math to see whether the interest savings still exceed the penalty.
Should I get a cosigner on a loan?
A cosigner can help you qualify or get a lower rate if your credit or income is thin, because the lender counts their credit and income too. The trade-off is real: the cosigner is legally on the hook if you miss a payment, the loan appears on their credit report, and it can limit their own borrowing capacity. Only use a cosigner if you're confident you can repay on your own and you've had a frank conversation about the risk.
When does it make sense to refinance a loan?
Refinancing usually pays off when you can drop your rate by roughly 1 percentage point or more, when your credit has improved substantially since you borrowed, or when you want to switch from a variable to a fixed rate. Always compare the total interest saved against the closing costs and any prepayment penalty on the existing loan. Our refinance calculator shows the break-even point in months.
How do I choose the right loan term?
Shorter terms mean higher monthly payments but dramatically less total interest; longer terms lower the monthly payment but can double or triple the interest paid. A useful rule: pick the shortest term where the monthly payment fits comfortably inside your budget with room for an emergency fund and other savings. On a mortgage, going from 30 to 15 years can cut lifetime interest by more than half; on an auto loan, staying at 60 months or less prevents you from being underwater on the car.
What happens if I make extra payments?
Extra payments go directly toward the principal, which lowers the balance that interest is calculated on for every remaining month. This both shortens the loan and slashes total interest paid — often by thousands. Even $50–$100 extra per month can shave years off a mortgage. Use the 'Extra Monthly Payment' field above to see the exact impact on your loan.
Personal loan versus auto loan — which is cheaper for a car?
Auto loans are almost always cheaper because they're secured by the vehicle — expect roughly 6–9% versus 10–18% on an unsecured personal loan. The only cases where a personal loan wins are older or private-sale cars that don't qualify for standard auto financing, or borrowers with very strong credit and existing bank relationships. Our car loan vs personal loan guide walks through the trade-offs.
How much loan can I actually afford?
A common benchmark: total monthly debt payments (including the new loan, mortgage, minimums on other debt) should stay under 36% of your gross monthly income, and non-mortgage debt under 15–20%. Beyond the ratio, make sure the payment still leaves room for saving at least 10–15% of income and covering surprise expenses. If the payment forces you to raid your emergency fund, the loan is too big.
How does taking out a loan affect my credit score?
Short term, the hard credit inquiry usually drops your score 5–10 points, and the new account lowers your average account age. Long term, on-time monthly payments build a strong payment history (35% of your FICO score) and adding an installment loan can improve your credit mix. Missed payments do the opposite — a single 30-day late payment can drop your score by 60–100 points and stay on the report for seven years.
Fixed rate versus variable rate — which is safer?
Fixed rates lock in the same payment for the life of the loan, so you're protected if market rates rise — the trade-off is a slightly higher starting rate. Variable rates start lower but reset periodically, so your payment can jump if benchmark rates rise. Choose fixed when you value predictability or expect to hold the loan more than 3–5 years; consider variable only for short-term loans or when you're confident rates will fall.
Does this calculator work for mortgages, auto, and personal loans?
Yes. The amortization math is identical for any fixed-rate installment loan — mortgages, auto loans, personal loans, student loans, RV loans, and small business term loans. Just enter the amount, rate, and term. For mortgages you'll want to add taxes, insurance, and PMI separately (use the mortgage calculator for a full PITI breakdown); for auto loans, factor in sales tax and any trade-in with the auto loan calculator.
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Disclaimer: This calculator provides estimates only and is not financial advice. See how our calculators work for the formulas and assumptions used. Actual loan terms, fees, and payments may vary — consult a qualified lender before borrowing.