Calculate monthly payments, APR, total cost and payoff date for any loan. Model extra payments, compare up to three loan offers, run bi-weekly acceleration, and handle balloon or interest-only structures in one tool.
- Monthly Payment
- Extra Payments
- Bi-Weekly vs Monthly
- Compare 3 Loans
- Balloon / Interest-Only
- Full Amortization
Uses the loan details from the Standard Loan tab above. Model three types of extra payments against the base schedule.
Compares a standard monthly schedule against a bi-weekly schedule paying half the monthly payment every two weeks. That equals 26 half-payments per year = 13 full payments.
Uses the loan details from the Standard Loan tab above. No additional inputs required here — press Calculate to see the comparison.
Compare three loan offers side by side. Each offer has its own amount, rate, term and fees. The calculator returns monthly payment, total interest, total cost and effective APR for each.
Model loans with an interest-only period, a balloon payment at the end, or both. Common for auto loans with balloon structures, business loans and some personal credit lines.
Results are at rest
Enter your loan details and press Calculate Loan.
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Yearly principal vs interest
Breakdown
What Makes a Loan Calculator Advanced
Basic loan calculators return one number: the monthly payment. That figure alone cannot tell you whether a loan is a good deal. An advanced calculator adds four things that actually change the decision.
APR, not just rate
The interest rate excludes lender fees. APR includes them. A 9.5% loan with $500 in fees can cost more than a 10% loan with no fees — APR is the only fair comparison.
Total cost over life
Two loans with the same monthly payment can differ by thousands in total interest. Total cost = principal + total interest + fees. It is the number that matters most.
Payoff acceleration
Extra payments reduce principal directly. A $100 per month extra on a 5-year $25,000 loan at 9.5% saves over $900 in interest and cuts the loan by 7 months.
Structure flexibility
Bi-weekly payments, balloon structures, interest-only periods — these change how much you pay and when. A serious tool handles all three.
How the Calculator Works
Every mode uses the standard amortization formula. Extra payments and special structures are applied month by month so the results are exact to the cent.
Base payment
Standard amortization formula gives the base monthly payment from principal, rate and term.
Monthly amortization
The loan is simulated month by month. Each month's interest is calculated on the remaining balance, and the rest reduces principal.
Extra payments applied
Any extra payment reduces principal in the same month, which removes interest from every remaining month.
Frequency adjustment
Bi-weekly and weekly schedules are modelled as equivalent monthly extra payments — 13 or 26 full payments per year.
APR calculation
APR is solved numerically so the present value of all payments equals the loan amount minus upfront fees.
Special structures
Interest-only periods pay only the interest each month. Balloon payments settle the remaining balance at the end of the term.
Worked Example — $25,000 at 9.5% for 48 months
| Scenario | Monthly payment | Months to payoff | Total interest | Interest saved |
|---|---|---|---|---|
| Base 48-month loan | $627.68 | 48 | $5,128.64 | — |
| +$100/month extra | $727.68 | 41 | $4,308.62 | $820.02 |
| +$200/month extra | $827.68 | 35 | $3,675.19 | $1,453.45 |
| Bi-weekly ($313.84 every 2 wk) | $627.68 effective | 44 | $4,687.35 | $441.29 |
| +$1,000/yr annual extra | $627.68 + $83.33/mo avg | 42 | $4,436.20 | $692.44 |
The front-loaded interest curve. On the base loan, over 60% of the total interest is paid in the first 24 months. That is why early extra payments have a disproportionate effect — they remove interest from every remaining month.
Bi-Weekly Payments Explained
Bi-weekly is marketed as a special "accelerated" payment plan. It is not magic — the whole benefit comes from the arithmetic of the calendar. There are 26 bi-weekly periods in a year, not 24, so paying half your monthly payment every two weeks adds up to 13 full monthly payments per year instead of 12.
The 26 vs 24 rule
365 days ÷ 14 = 26.07 bi-weekly periods per year. Pay half your monthly every two weeks and you make one extra full payment per year.
Equivalent to 8.33% extra
The extra payment per year works out to about 8.33% more paid annually. On a 5-year loan, that typically saves 3–5 months and several hundred dollars of interest.
Beware the fee
Many lenders charge a setup fee to switch to bi-weekly, and some third-party services charge $300–$500. You can get the exact same result for free by paying 1/12 extra on your monthly payment.
Better for weekly earners
If you are paid weekly or bi-weekly, the schedule matches your income and removes the discipline problem of saving for a monthly payment.
APR vs Interest Rate: The Real Comparison
Lenders quote the interest rate because it looks smaller. They rarely lead with APR because it includes the fees you pay. When comparing two loans, always use APR.
| Loan | Amount | Rate | Fees | APR | Which is cheaper? |
|---|---|---|---|---|---|
| Loan A | $25,000 | 8.5% | $500 | 9.05% | Better despite higher rate |
| Loan B | $25,000 | 8.0% | $1,800 | 9.68% | Worse due to higher fees |
| Loan C | $25,000 | 9.0% | $0 | 9.00% | Best overall |
| Loan D | $25,000 | 7.5% | $2,500 | 9.55% | Worse despite lowest rate |
A 1% lower interest rate saves about 0.5% of the loan balance in annual interest — on $25,000, that is roughly $125 per year. If the lower-rate loan carries $500 more in fees, it takes four years to break even. On short loans, fees matter more than the rate.
The Power of Extra Payments on Any Loan
Extra payments reduce principal directly, and the effect compounds. Here is what happens across common loan sizes and terms when you pay extra from month one.
| Loan | Base payment | Extra $100/mo | Interest saved | Months saved |
|---|---|---|---|---|
| $15,000 auto @ 7% for 60 mo | $297 | $397 | $520 | 9 mo |
| $25,000 personal @ 9.5% for 48 mo | $628 | $728 | $820 | 7 mo |
| $35,000 auto @ 6.5% for 72 mo | $588 | $688 | $1,140 | 11 mo |
| $50,000 student @ 5.5% for 120 mo | $543 | $643 | $2,020 | 18 mo |
| $100,000 business @ 8% for 84 mo | $1,558 | $1,658 | $2,680 | 12 mo |
The pattern is consistent: every $100 of extra monthly payment saves roughly $500–$2,500 in interest and cuts 6–18 months off the term, depending on the loan size and rate. The effect is largest on long-term, high-balance loans because there is more interest to remove.
Loan Type Notes
Auto loans
Typically 36–84 months. Simple interest, fixed payment. Watch for prepayment penalties on subprime auto loans — they eliminate the benefit of extra payments.
Personal loans
Unsecured, 2–7 years, rates from 6% to 36% depending on credit. Fixed-rate and fixed-term. Often carry origination fees of 1–8% of the loan.
Student loans
Federal loans have fixed rates set annually and income-driven repayment options. Private student loans follow consumer lending rules. Extra payments always apply to principal.
Business loans
Wider range of structures — term loans, SBA loans, lines of credit. May have variable rates tied to prime. Some term loans have interest-only periods and balloon payments.
Balloon loans
A low monthly payment for the term, then the remaining balance due at the end. Common on auto and business loans. Risky if you cannot refinance or pay the balloon.
Interest-only loans
Pay only interest for a set period, then principal and interest for the remainder. Lower early payments but higher later payments. Rare in consumer lending, common in business and investor loans.
APR calculation follows Truth in Lending Act (TILA) and Regulation Z (12 CFR 1026). Amortization uses the standard annuity formula from the FNMA and FHLMC servicing guides. Prepayment penalties are restricted by Dodd-Frank Wall Street Reform and Consumer Protection Act, Section 1414. Auto loan prepayment rules follow state-specific retail instalment sales acts.
Compare loans on APR, not interest rate — the fees matter as much as the rate on short loans. On any loan over 36 months, $100 per month extra saves $500–$2,500 in interest. A 1% lower rate saves about 0.5% of the balance per year in interest, so on $25,000 that is $125/year. Always check whether the loan has a prepayment penalty before planning extra payments — that one clause can eliminate all the interest savings.
People Also Ask
How is a loan payment calculated?
Use the standard amortization formula: M = P × r(1+r)^n ÷ ((1+r)^n − 1), where P is the loan amount, r is the monthly interest rate (annual rate ÷ 12), and n is the number of monthly payments. This gives a fixed payment that fully pays off principal and interest by the end of the term.
What is APR and why does it matter more than the interest rate?
APR (Annual Percentage Rate) includes the interest rate plus most lender fees spread across the loan term. The interest rate tells you the cost of the money itself. The APR tells you the true cost of borrowing. A 7.5% loan with $2,500 in fees can have a higher APR (and cost more) than a 9% loan with no fees. Always compare APR across loans.
How do extra payments affect my loan?
Extra payments reduce the principal balance directly, which removes interest from every remaining month. On a $25,000 loan at 9.5% for 48 months, adding $100 per month saves about $820 in interest and pays the loan off 7 months early. The earlier in the loan you start, the bigger the effect — most of the interest is front-loaded.
Is bi-weekly payment worth it?
Only if the lender does not charge a setup fee. Bi-weekly works because there are 26 two-week periods in a year, so paying half the monthly payment every two weeks adds up to 13 full payments per year instead of 12. You get the exact same result for free by paying 1/12 extra on your monthly payment — no switching fee, no third-party service, same interest savings.
What is a balloon payment loan?
A balloon loan has lower monthly payments during the term but requires a large lump-sum payment (the "balloon") at the end. Auto loans with balloons are common — you pay a small monthly amount for 3–5 years and then owe the residual value of the car. Business loans often use balloon structures too. The risk is being unable to pay or refinance the balloon when it comes due.
What is an interest-only loan?
An interest-only loan lets you pay only the interest for a set period (typically 5–10 years), then the full principal and interest for the remaining term. The early payment is lower but the later payment is much higher. Common in investment property and business loans where cash flow is expected to improve. Rare in consumer lending for good reason — the payment shock at the end is severe.
How do I compare two loan offers fairly?
Compare on four numbers: APR, monthly payment, total interest paid, and total cost of borrowing (principal + interest + fees). A loan with a lower monthly payment but a longer term usually costs more overall. A loan with a lower rate but higher fees can be more expensive than a higher-rate loan with no fees. The Compare tab above runs all four for three loans side by side.
What happens if I miss a loan payment?
Most consumer loans allow a 10–15 day grace period before a late fee applies (typically 3–5% of the payment or a flat fee). Missing a payment also triggers a negative mark on your credit report after 30 days. Two consecutive missed payments typically start the default process, and three to four usually triggers collection. Contact the lender immediately if you cannot pay — hardship programs exist before default.
Can I pay off my loan early without a penalty?
For most consumer loans in the US, yes — prepayment penalties are restricted by federal law (Dodd-Frank Section 1414) for most residential mortgages and often prohibited by state law for auto and personal loans. But some subprime auto loans and many business loans do carry prepayment penalties. Read the loan agreement for a "prepayment penalty" or "minimum interest charge" clause before planning extra payments.
Does the loan term affect total cost?
Yes, dramatically. A $25,000 loan at 9.5% costs $5,129 in interest over 48 months but $7,729 over 72 months. The longer term has a lower monthly payment ($458 vs $628) but you pay $2,600 more in interest overall. The trade-off is cash flow versus total cost. Choose the longest term you can afford to pay off early, not the one with the lowest required payment.
What credit score do I need for a good loan rate?
For personal loans, the best rates (under 8%) typically need a score above 720. Scores from 660–719 get mid-range rates (10–15%). Below 660 gets rates over 18%. For auto loans, the tiers are similar — super prime (781+) gets under 4%, prime (661–780) gets 5–7%, subprime (501–600) gets 12%+. A 100-point difference in credit score changes the rate by 2–4%.
Should I choose a fixed or variable rate loan?
Fixed-rate for anything over 36 months. Variable rates start lower but reset periodically based on a benchmark index (like SOFR or prime). In a rising-rate environment, variable can double your payment over the loan term. Fixed gives certainty. Variable can work if you are confident you will pay off the loan within the initial fixed period, but that is a bet most borrowers should not take.
How do lenders calculate how much I can borrow?
Using the debt-to-income (DTI) ratio. Total monthly debt payments (including the new loan) should be under 36–43% of gross monthly income. The lender also checks credit score, employment history, existing assets and the loan's purpose. For auto loans, lenders usually cap the loan at 100–120% of the vehicle value. For personal loans, most lenders cap at $50,000 and require income proof above $25,000.
Is this calculator free and does it store my data?
Yes and no. Every calculation runs entirely in your browser — nothing is sent to a server, nothing is stored. Your inputs are not saved anywhere. The only thing remembered is the rating counter, which uses your browser's local storage and never leaves your device.
Related Calculators
References
- Consumer Financial Protection Bureau. Regulation Z — Truth in Lending Act disclosure requirements (12 CFR 1026). CFPB, current edition.
- Dodd-Frank Wall Street Reform and Consumer Protection Act, Section 1414 — Prepayment penalty restrictions. U.S. Congress.
- Federal Housing Finance Agency. Servicing Guide — standard amortization methodology. FHFA, current edition.
- Federal Reserve. Consumer Credit — G.19 Statistical Release — quarterly average loan rates by product type.
- National Institute of Standards and Technology. NIST Handbook 44 — measuring device standards referenced for financial calculator definitions.
This calculator provides estimates only and is not a loan offer or commitment to lend. Your actual rate, monthly payment and fees depend on your lender, credit score and full financial picture. Always compare Loan Estimates from at least three lenders before committing.