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 (the note rate, not the APR)
Use the interest rate from your loan estimate or note — quoted yearly, charged monthly at one-twelfth of it. The APR is a different number: Regulation Z defines it as a measure of the cost of credit, as a yearly rate, that relates the amount and timing of what you receive to the amount and timing of what you pay, so it also carries fees and points and runs above the note rate. Adjustable-rate loans use the current rate; the schedule won't reflect future resets.
Enter the term in years or months
Mortgages commonly run 15 or 30 years (the two terms Freddie Mac surveys weekly); car and personal loans are usually counted in 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 last payment move earlier and total interest drop — by tens of thousands on a 30-year mortgage. The extra is paid with every instalment from the first and goes entirely to principal. Dates assume the first payment falls next month.
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. The payment does not split 50/50 until around month 233 — well into year 20 — and only in the final years is it 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 "the first years of a mortgage are mostly interest" rule of thumb is true and matters a lot. If you sell or refinance after five years, you've paid $113,772 toward the loan but only about $19,200 of it 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. It is the present value of an ordinary annuity solved for the payment — the derivation is in any corporate-finance textbook — and a fixed-rate lender's schedule is simply this formula iterated month by month. There is nothing proprietary about an amortization table.
Why Extra Payments Are So Powerful
A $200 extra monthly payment on a $300,000 / 30-year / 6.5% mortgage saves about $103,450 in total interest and pays the loan off 83 months — 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.
A 30-year mortgage of $300,000 at 6.5% carries $382,637 of interest. Add $200 a month and it falls to $279,187 — $103,450 less, and the loan ends 83 months sooner, for $55,200 of extra principal.
Bi-Weekly Payments — The Hidden Lever
Another acceleration tactic: pay half the instalment every two weeks. There are 26 fortnights in a year, not 24, so you pay the equivalent of 13 monthly payments instead of 12. On the same $300,000 / 30-year / 6.5% loan, one-twelfth of a payment extra each month saves about $87,259 and 5.8 years; a true bi-weekly schedule, with each half applied the day it is paid and interest accruing daily, saves about $90,421 and 6.0 years. The catch is in the word "applied": the CFPB found that one bi-weekly programme held the half-payments and paid the mortgage on its original monthly schedule, so any saving came only from the higher yearly payment. Ask your servicer when each payment is credited.
Refinance vs Extra Payment — When Each Wins
If rates drop far enough that the monthly saving repays the closing costs well before you expect to move or refinance again, refinancing usually beats extra payments because it lowers the rate 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.
Month one on a $300K mortgage pays $271 of principal
The PMT formula P·r·(1+r)ⁿ / ((1+r)ⁿ−1) is the present value of an annuity solved for the payment — the same equation behind every fixed-rate lender's schedule.
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: $382,637 — 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 carry lower rates — 6.71% versus 7.40% for the 30-year in Freddie Mac's survey of 15 October 2026 — so half the term costs far less than half the interest.
Bi-weekly payments = 13 monthly payments a year, not 12 — but the CFPB found a programme that held them and paid monthly anyway.
The 50/50 principal-interest crossover on a 30-year mortgage at 6.5% happens around month 233 — in year 20, not year 15.
Car loans on a reducing balance amortize the same way over a shorter term — interest still front-loads, just over fewer months.
US rules (12 CFR 1026.43(g)) let a fixed-rate qualified mortgage carry a prepayment penalty only in its first 3 years, capped at 2% then 1% of the amount prepaid — 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 month 233, in year 20.
- On a $300K / 30-year / 6.5% mortgage: $100/month extra saves about $61,000 of interest and 4 years; $200/month about $103,450 and 6 years 11 months; $500/month about $179,762 and 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. Damodaran's data (NYU Stern) put the S&P 500 with dividends at about 10% a year compounded over 1928–2025 before inflation: $100 at the start of 1928 grew to about $1.16 million. A 6.5% mortgage paid down early earns 6.5% with no market risk; the lower your rate, the more the comparison favours investing 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. The APR is a disclosure: Regulation Z (12 CFR 1026.22) defines it as "a measure of the cost of credit, expressed as a yearly rate", so it carries finance charges such as points and certain fees and is usually higher than the note rate. Use the note rate for the schedule and the APR to compare offers.
- 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 and extras, the schedule is computed to the cent, each month's interest rounded and the last payment settling the rounding, as a lender's would be. 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.
- For a US home loan covered by the ability-to-repay rule, a prepayment penalty is only permitted on a qualified mortgage whose APR cannot rise and which is not higher-priced; it cannot apply after the first three years, and is capped at 2% of the amount prepaid in years one and two and 1% in year three (12 CFR 1026.43(g)) — so on most loans 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.
Method & sources
How it computes
PMT = P·r(1+r)^n ÷ ((1+r)^n − 1), r = annual rate ÷ 12, rounded to the cent; then month by month in integer cents: interest = start-of-month balance × r (rounded), the payment plus any extra principal applied, the last payment settling the balance to 0. Extra saves = baseline − accelerated interest. Checked against the CFPB sample Loan Estimate H-24(B) ($162,000, 3.875%, 30 years: $761.78). Dates count from the Singapore business day (MortgageKernel.extraPayments).
What this tool implements
- Present value of an ordinary annuity solved for the payment; monthly compounding of the nominal annual rate
- Fixed-rate loans only; taxes, insurance, PMI and fees excluded (stated on page)
- Worked examples on the page are recomputed from the formula (US$300,000 / 6.5% / 30 yr: PMT US$1,896.20; total interest US$382,633; +US$200/mo saves US$103,449 and 83 months)
- Integer-cent schedule (RECATOOLS arithmetic): the instalment and each month's interest are rounded half-up to the cent; extra principal is paid with every instalment from month 1 and applied entirely to principal; the loan ends in the month the balance plus interest fits in what is due, and the last payment settles the balance to exactly 0. Totals, the CSV and the table are the same schedule.
- Dates: the first payment falls in the month after today on the Singapore business day (RecaBusinessDay), not the visitor's clock.
- APR wording follows Regulation Z, 12 CFR 1026.22(a)(1): the APR "is a measure of the cost of credit, expressed as a yearly rate"; the schedule takes the note rate. Prepayment limits from 12 CFR 1026.43(g): only a fixed-APR qualified mortgage that is not higher-priced, not after three years, at most 2% then 1% of the amount prepaid.
Sources
- Brealey RA, Myers SC, Allen F. Principles of Corporate Finance. 13th ed. McGraw-Hill; 2020. Chapter 2, How to calculate present values (annuity formula).
- Consumer Financial Protection Bureau. Regulation Z, 12 CFR §1026.43(g) Prepayment penalties (three-year limit; 2%/2%/1% caps). https://www.law.cornell.edu/cfr/text/12/1026.43
- Damodaran A. Historical Returns on Stocks, Bonds and Bills: 1928–2025. NYU Stern. https://pages.stern.nyu.edu/~adamodar/New_Home_Page/datafile/hist…
- Consumer Financial Protection Bureau. Regulation Z, 12 CFR 1026 Appendix H, form H-24(B) Mortgage Loan Transaction Loan Estimate — Fixed Rate Loan Sample. https://www.ecfr.gov/current/title-12/part-1026/appendix-Appendix…
- Regulation Z, 12 CFR 1026.22 Determination of annual percentage rate. https://www.ecfr.gov/current/title-12/chapter-X/part-1026/subpart…
- Regulation Z, 12 CFR 1026.43(g) Prepayment penalties. https://www.ecfr.gov/current/title-12/chapter-X/part-1026/subpart…
- Freddie Mac. Primary Mortgage Market Survey, history file, week of 15 October 2026 (30-yr FRM 7.40%, 15-yr FRM 6.71%). https://www.freddiemac.com/pmms/docs/PMMS_history.csv
- Consumer Financial Protection Bureau. Consent order, In re Paymap Inc., 2015-CFPB-0017 (bi-weekly debits held and paid on the monthly schedule). https://files.consumerfinance.gov/f/201507_cfpb_consent-order_pay…
What can make this go out of date
- Freddie Mac PMMS weekly rates quoted in fact 05 (moves weekly)
- none at runtime — the calculator hardcodes no rate or rule
Abridged — the full review record for this tool runs longer than the list above.
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