Loan Amortization Schedule Generator
Loan amortization calculator. Generate a full month-by-month payment schedule with principal/interest split, total interest, payoff date. Extra payments supported. Print/CSV export.
Loan Amortization Schedule Generator
Generates a complete month-by-month amortization table for any fixed-rate loan — mortgage, auto, personal, or business. Shows exactly how each payment splits between interest (front-loaded) and principal (back-loaded), the running balance, and the interest you save when you add extra monthly payments.
Payment schedule
—| # | Date | Payment | Principal | Interest | Balance |
|---|
How to Use the Loan Amortization Calculator
Enter the loan amount (principal)
The full principal balance at the start of the loan. For a mortgage, this is the price minus your down payment plus closing costs you rolled in. For an auto loan, it's the contract amount before any prepayment. For a refinance, use the new loan amount, not the old balance.
Set the annual interest rate (APR)
Use the rate from your loan estimate or note — quoted annually but applied monthly (the calculator handles the conversion). For US mortgages, APR includes points and certain fees; for purely amortization math, the note rate is enough. Adjustable-rate loans use the current rate; the schedule won't reflect future resets.
Enter the term in years or months
Most mortgages run 15 or 30 years; auto loans 36–84 months; personal loans 24–60 months. The dropdown toggles units. The shorter the term, the higher the monthly payment but the lower total interest — the spread is dramatic across longer loans.
Add extra monthly payment (optional)
Try $100, $200, $500. Watch the payoff date shift earlier and total interest drop — sometimes by tens of thousands on a 30-year mortgage. Extra payments go entirely to principal, accelerating amortization. The payment count shows months saved.
How Loan Amortization Actually Works
The Front-Loaded Interest Pattern
Amortization isn't a 50/50 split between principal and interest at any point in the loan. In the early years, interest dominates: on a $300,000 loan at 6.5% over 30 years, your first month's payment of $1,896 is roughly $1,625 interest and only $271 principal. By year 15, it's about 50/50. By year 28, it's nearly all principal. The reason is purely mathematical — interest each month is calculated against the remaining balance, and the balance starts at its maximum and falls. The payment stays constant only because the math is engineered to make it so.
This is why the "first half of a mortgage is interest" rule of thumb is roughly true and matters a lot. If you sell or refinance in year 5, you've paid most of $113,760 toward the loan but only about $19,000 came off the principal. The lender got the interest first. That's not predatory — it's the only way to keep payments level on a declining balance — but it shapes every refinance and prepayment decision you'll make.
The Math (PMT Formula)
The standard monthly payment formula: PMT = P · r · (1+r)ⁿ / ((1+r)ⁿ − 1), where P is principal, r is the monthly interest rate (annual ÷ 12), and n is the total number of payments. For each subsequent month: interest = balance × r, principal = PMT − interest, balance -= principal. The formula was derived in 18th–19th-century financial mathematics and hasn't changed — every US/CA/UK retail lender uses the same equation. There's nothing proprietary about an amortization table; the table itself is just iterating the formula.
Why Extra Payments Are So Powerful
A $200 extra monthly payment on a $300,000 / 30-year / 6.5% mortgage saves about $103,000 in total interest and pays the loan off nearly 7 years early. The mechanism: each extra dollar of principal eliminates all future interest that would have accrued on that dollar over the remaining life of the loan. Early extras are dramatically more valuable than late extras — a $200 payment in year 1 saves much more interest than the same $200 in year 25, because year-1 dollars compound interest savings over 29 more years. The first 10 years of extras do most of the work.
"Standard 30-year mortgage, $300K @ 6.5%: total interest $383K. Add $200/month extra: total interest drops to $279K — savings of $103K, plus you finish nearly 7 years sooner. The 'cost' of those extras: $200 × 277 months ≈ $55K of extra cash flow committed early."
Bi-Weekly Payments — The Hidden Lever
One of the most popular acceleration tactics: switch from monthly payments to bi-weekly half-payments. Since there are 26 bi-weekly periods per year (not 24), you end up making the equivalent of 13 monthly payments instead of 12 — effectively one full extra payment each year. On the same $300K / 30-year / 6.5% example, bi-weekly accelerates payoff by about 4–5 years and saves roughly $65K in interest. The catch: many servicers don't actually apply payments bi-weekly — they bank the half-payments and apply them monthly, killing the effect. Verify your servicer credits the extra payment to principal in the same period it's received.
Refinance vs Extra Payment — When Each Wins
If rates drop materially (typically ≥ 0.75 percentage points), refinancing usually beats extra payments because you reset the math on the entire remaining balance. If rates haven't dropped, extra payments win by default — they cost nothing to "start" (no closing costs, no fees) and the savings compound from month one. A common hybrid for sophisticated borrowers: refinance when rates drop, then immediately direct the savings as extra payments on the new loan. That captures both the rate reduction and the acceleration in one move.
10 Facts About Loan Amortization
The PMT formula P·r·(1+r)ⁿ / ((1+r)ⁿ−1) has been used since the 19th century — every retail lender uses it.
First-month interest on a $300K / 6.5% / 30-year mortgage: about $1,625. Principal: only $271.
Total interest on the same loan over 30 years: about $382,000 — more than the original principal.
A $200/month extra payment on that loan saves about $103K interest + nearly 7 years off the term.
15-year mortgages typically have rates 0.5–0.75% lower than 30-year — half the term, less than half the interest.
Bi-weekly payments = 13 monthly payments per year, not 12 — but only if your servicer applies them correctly.
The 50/50 principal-interest crossover on a 30-year mortgage at 6.5% happens around month 180 (year 15).
Auto loans amortize the same way but over 36–84 months — interest still front-loads, just over a shorter window.
Most US mortgages have no prepayment penalty after the first 3 years — verify in your note before adding extras.
For an adjustable-rate mortgage (ARM), the schedule resets when the rate changes — this calculator shows fixed-rate only.
Frequently Asked Questions
- Yes — it uses the standard amortization formula, which is identical for mortgages, auto loans, personal loans, and most fixed-rate business loans. The only exception is interest-only loans (where the early payments cover only interest), balloon loans (which end with a large lump-sum payment), and adjustable-rate loans (where the rate changes mid-term). For those, you'd need to model each phase separately.
- Each month's interest is calculated against the remaining balance, and at the start of the loan the balance is at its maximum. As you pay down principal, the interest portion shrinks and the principal portion grows. The payment stays constant only because the math is engineered to make it so — on a 30-year mortgage at 6.5%, you don't reach a 50/50 split until around year 15.
- On a $300K / 30-year / 6.5% mortgage: $100/month extra saves about $61K interest + 4 years; $200/month saves about $103K + nearly 7 years; $500/month saves about $180K + 12.5 years. Early extras are worth dramatically more than late extras because the savings compound over the remaining life of the loan. The first 10 years of extras do most of the heavy lifting.
- No — only principal and interest (P&I). Property taxes, homeowners insurance, PMI, and HOA fees are escrowed by your servicer but are not part of the amortization itself. Your total monthly payment (PITI) will be higher than this calculator shows. For mortgage planning, multiply property value by your local tax rate and add insurance + PMI separately.
- A guaranteed risk-free return equal to your mortgage rate vs an uncertain market return is the comparison. At 6.5% mortgage rates, paying down the mortgage roughly matches the long-run S&P 500 real return (~7%) with zero risk. If your rate is below 4%, investing usually wins over long horizons. Many people split — invest the bulk and add modest extras to the mortgage for psychological and balance-sheet benefits.
- The note rate is what the lender uses to compute monthly interest — this calculator wants the note rate. APR is a regulatory disclosure that bundles the note rate with points and certain fees to give a single comparable figure across lenders. For pure amortization math, use the note rate. For comparing competing loan offers, use APR.
- A few common reasons: (1) your servicer escrows taxes + insurance into the monthly payment, (2) ARM rate already reset, (3) the loan uses 360-day vs 365-day interest accrual conventions, (4) you have an interest-only or balloon component, (5) PMI hasn't dropped off yet. The calculator shows pure P&I on a fixed-rate amortizing schedule — your actual statement will often include escrows on top.
- Yes — click Export CSV below the summary. The CSV opens directly in Excel, Google Sheets, or any spreadsheet tool. It includes the input summary at the top + the full payment table below. The Print button generates a clean printable version suitable for filing with loan documents.
- For fixed-rate loans with consistent monthly payments + consistent extras, the calculator is mathematically exact — within rounding noise of a penny. The biggest sources of real-world drift: missed or late payments (which add interest), additional principal payments made off-schedule (which need to be re-modeled), and servicer-side payment-application policies. Always verify the projected payoff against your servicer's own balance statement.
- Most US residential mortgages have no prepayment penalty after the first 3 years — extras are free to make. Auto loans, personal loans, and some business loans may have prepayment penalties; commercial mortgages often have substantial ones (yield maintenance or defeasance). Check your loan note for "prepayment provisions" before committing to an aggressive extra-payment schedule.
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