Amortization Schedule: How Your Payments Really Split
Published: August 2, 2026 | Updated: August 2, 2026 | Reading time: 16 minutes
By James Chen | Reviewed by NMLS-licensed mortgage professionals
Your First Payment Is 86% Interest
Take a $350,000 mortgage at 6.625% for 30 years. Your payment is $2,241.09 every month. In month one, $1,932.29 of that goes to interest and $308.80 goes to principal. You borrowed $350,000, paid $2,241, and your balance dropped by less than $310.
That's amortization — the math that mortgages run on. Every payment is split into interest and principal, and the split is heavily tilted toward interest at the start. This isn't a lender trick. It's how any loan with a fixed payment and a fixed rate works, from a car loan to a student loan. But the scale of it surprises almost everyone, so it's worth understanding precisely: what the schedule looks like, why it's built this way, and what you can do about it.
This guide walks through a real amortization schedule line by line — the only way to actually see where your money goes — then shows how extra payments change the whole curve.
How Amortization Math Works
The formula behind every amortizing loan is built on one idea: you pay interest on whatever you still owe, every month. The payment is calculated once, at closing, so that the loan is exactly paid off after 360 monthly payments (30 years). Because the payment is fixed, the split between interest and principal has to move over time:
- Month 1: you owe $350,000. Interest for the month is $350,000 × 6.625% ÷ 12 = $1,932.29. The remaining $308.80 of your payment reduces principal.
- Month 2: you owe $349,691.20. Interest drops to $1,930.59. Principal share rises to $310.50.
- Every month after: the balance is a little smaller, so interest is a little smaller, so principal is a little bigger. The payment never changes.
That's the whole engine. No lender is front-loading interest to collect more from you — interest is front-loaded because the balance is front-loaded. You owe the most at the beginning, so the interest charge is largest at the beginning. The flip side: every extra dollar of principal you pay early removes a dollar that would have generated interest for the remaining decades of the loan.
The same logic applies at any rate. The lower your rate, the flatter the curve; the higher your rate, the steeper. At 3% the first payment on this loan would be $875 interest and $601 principal — a 59/41 split. At 6.625% it's 86/14. Rate environment isn't just about payment size. It shapes how fast you build equity.
The Schedule, Year by Year
Here's what a 30-year amortization schedule actually does to a $350,000 loan at 6.625%, sampled at four points:
| Year | Interest Paid (yr) | Principal Paid (yr) | Interest Share | Ending Balance |
|---|---|---|---|---|
| Year 1 | $23,073 | $3,820 | 86% | $346,180 |
| Year 5 | $21,917 | $4,976 | 81% | $328,106 |
| Year 10 | $20,255 | $6,638 | 75% | $300,931 |
| Year 15 | $17,260 | $9,633 | 64% | $255,251 |
| Year 20 | $12,807 | $14,086 | 48% | $201,485 |
| Year 25 | $6,534 | $20,359 | 24% | $128,230 |
| Year 30 | $941 | $25,952 | 4% | $0 |
$350,000 loan, 6.625% fixed, 30 years. Monthly P&I: $2,241.09. Year 10 and Year 20 figures interpolated from standard schedule; totals verified against full 360-payment run.
Three things jump out. First, after five years and $134,465 in payments, your balance is down only $21,894 — you've paid off 6% of the loan. Second, the crossover — where principal finally exceeds interest in a given year — doesn't happen until year 21 (month 250, to be exact). Third, the total bill: $806,792 over 30 years, of which $456,792 is interest on a $350,000 loan.
The First Five Years: 84% Interest
Add up the first 60 payments and you get a number that makes people rethink their down payment:
| Window | Total Paid | Interest | Principal | Interest Share |
|---|---|---|---|---|
| First 5 years | $134,465 | $112,571 | $21,894 | 84% |
| First 10 years | $268,931 | $215,523 | $53,408 | 80% |
| First 15 years | $403,396 | $306,393 | $97,003 | 76% |
| Entire 30 years | $806,792 | $456,792 | $350,000 | 57% |
$350,000 at 6.625%, 30-year fixed. The widely cited figure — that roughly 80% of your first decade of payments is interest — holds here: 80% for years 1–10, 84% for years 1–5.
The common rule of thumb says the first five years of a 30-year mortgage are about 80% interest. At today's 6.625%, it's 84%. That has a practical implication: in the early years, you're buying the option on a house more than the house itself. Your equity grows through your down payment and market appreciation, not through your monthly bill. If you sell after three years, most of what you paid went to the lender, not into your pocket — which is exactly why the rent-versus-buy math depends so heavily on how long you stay.
How to Read an Amortization Schedule
Your lender will hand you an amortization schedule at closing, and you'll see a table with 360 rows. Most people file it away. Here's what to actually look at:
- Columns to care about: payment number, payment amount, interest, principal, balance. Ignore the rest.
- Scan the last column (balance): find the row where your balance hits 80% of the original loan — that's when you can request PMI removal on a conventional loan. On this loan, 80% of $350,000 is $280,000, which happens around month 57. That's the row that saves you $180–$250 a month.
- Find the crossover month: the row where principal finally exceeds interest. On this loan it's month 250 — year 21. Anything you do before then to pay extra shifts that crossover earlier.
- Total interest: the sum of the interest column. $456,792 here. That's the number every prepayment strategy is fighting.
You don't need to wait for a paper schedule. Our mortgage calculator shows the full payment math, and any amortization calculator will reproduce the schedule to the cent — the formula is standardized.
What Extra Payments Actually Do
Because interest is calculated on the remaining balance, an extra dollar of principal today kills interest on that dollar for every remaining year of the loan. Here's the payoff table for the same $350,000 loan at 6.625%:
| Extra Payment | Payoff Time | Years Saved | Total Interest | Interest Saved |
|---|---|---|---|---|
| $0 / month | 30.0 years | — | $456,792 | — |
| $50 / month | 28.1 years | 1.9 | $421,525 | $35,267 |
| $100 / month | 26.4 years | 3.6 | $392,067 | $64,725 |
| $250 / month | 22.7 years | 7.3 | $326,289 | $130,502 |
| $500 / month | 18.5 years | 11.5 | $257,681 | $199,111 |
| One extra payment / year | 24.1 years | 5.9 | $350,745 | $106,047 |
$350,000 at 6.625%, 30-year fixed. "One extra payment/year" = $2,241.09 additional principal annually, spread monthly. Results computed with a full amortization run.
$100 a month — roughly the cost of a streaming bundle plus a takeout order — buys you 3.6 years and $64,725. The one-extra-payment-per-year strategy (which the biweekly payment method automates) saves $106,047. The pattern is the same for every row: the earlier the extra dollar lands, the more interest it kills. A $1,000 lump sum in year one saves about $6,200 over the life of the loan; the same $1,000 in year 20 saves about $900.
One caution: check your loan documents before sending extra money. Most conventional loans accept principal prepayments freely, but some lenders apply the extra to next month's scheduled payment unless you write "apply to principal" on the check or set it in your online portal. FHA and VA loans have their own rules, and some states restrict prepayment penalties on certain loan types. For the full strategy playbook, see our guide to paying off your mortgage early.
Why the Schedule Looks Different on a 15-Year Loan
A 15-year mortgage is the same amortization engine with a much faster burn rate. On $350,000 at 6.625% for 15 years, the payment is $3,069 and the crossover — principal exceeding interest — happens in year 8 instead of year 21. Total interest: about $202,000 instead of $456,792. You're paying roughly $828 more per month to save a quarter-million dollars and 15 years. The full comparison is in our 15-year vs 30-year analysis.
The tradeoff is liquidity. The 15-year forces you to save through your payment; the 30-year with disciplined extra payments gives you the option to stop prepaying in a bad month. That optionality has real value if your income is uneven. The math, though, doesn't care about feelings — a 30-year loan paid like a 15-year (same total monthly) produces nearly identical results, because amortization responds to principal, not to the label on the loan.
Amortization and Refinancing: The Reset Trap
Refinancing creates a brand-new amortization schedule. Say you're five years into this $350,000 loan with a balance of $328,106. If you refinance into another 30-year term at 6.25%, you restart the clock: your new first payment will be roughly 86% interest again, and the payoff date extends back to 30 years from the refi date. That's fine if you're cutting your rate, but it's why the refinance calculator matters — you need the monthly savings to outweigh the interest you're re-front-loading.
The common fix: refinance into a shorter term, or keep paying your old monthly amount after a rate-and-term refi. If your payment drops $150 and you keep sending the old amount, the extra $150 goes to principal and the schedule accelerates dramatically. The breakeven math is the same either way — closing costs divided by monthly savings — but how you handle the freed-up cash decides whether you actually win.
Amortization on Other Loan Types: ARM, Interest-Only, Biweekly
Not every mortgage runs on the classic 30-year fixed schedule, and the differences matter when you're reading a statement.
Adjustable-rate mortgages (ARMs) amortize like a fixed loan during the initial fixed period — say, 5 or 7 years — then recast at each adjustment. When the rate resets, the lender recalculates the payment so the loan still pays off by the original maturity date. A rate jump from 5.875% to 7.25% at the first adjustment doesn't just raise your interest charge; the payment is recomputed to finish on schedule, so the increase is larger than the pure rate difference. The ARM vs. fixed analysis covers when that trade makes sense.
Interest-only loans do exactly what the name says for a set period — typically 5 to 10 years, you pay only interest, and the balance doesn't move. When the interest-only period ends, the loan recasts into a fully amortizing payment for the remaining term. A $350,000 interest-only loan at 6.625% costs $1,932 a month during the interest-only window — $309 less than the amortizing payment — and then jumps to a payment sized to retire the entire balance in the remaining years. The recast payment can be substantially higher than the original amortizing payment would have been, which is how interest-only loans surprise people. Our interest-only guide runs the full example.
Biweekly schedules compress the amortization curve by making 26 half-payments a year instead of 12 full ones — one extra principal payment annually. On this $350,000 loan, the standard schedule pays off in 360 months; the biweekly version finishes in roughly 289 months and cuts interest from $456,792 to about $350,745. The full math — including why the paid biweekly programs are usually a waste of money — is in our biweekly payments breakdown.
The Spreadsheet Method: Build Your Own Schedule
You can reproduce any lender's amortization schedule in a spreadsheet in under a minute, and doing it once cements how the math works. Three functions do all the work:
| Function | What It Returns | Example ($350,000, 6.625%, 30yr) |
|---|---|---|
| =PMT(rate/12, nper, pv) | Monthly payment | $2,241.09 |
| =IPMT(rate/12, period, nper, pv) | Interest portion of payment N | Period 1: $1,932.29 |
| =PPMT(rate/12, period, nper, pv) | Principal portion of payment N | Period 1: $308.80 |
Spreadsheet formulas use the periodic rate (annual ÷ 12), the payment number, the total number of payments (360), and the loan amount. IPMT + PPMT always equals PMT.
Build 360 rows with a balance column and you have the full schedule — then change the rate or add an extra payment column and watch the payoff date move. It's the fastest way to test "what if I pay $200 extra starting in year three?" without trusting an online tool. When your lender's year-end statement arrives, your spreadsheet should match it to the penny; if it doesn't, ask why. Discrepancies are rare and almost always traceable to escrow, which sits outside the amortization schedule.
The 78% Rule: The PMI Row on Your Schedule
One row of the amortization schedule is worth real money if you bought with less than 20% down: the row where your loan balance hits 78% of the original home value. On a conventional loan, the lender must automatically cancel PMI when your balance reaches 78% of the original purchase price — that's federal law (the Homeowners Protection Act of 1998). You can also request cancellation at 80%, and on many loans you can cancel even earlier if your home has appreciated and you pay for a new appraisal.
On the $350,000 loan in this guide, 78% is a $273,000 balance — reached around month 57 under the standard schedule. At that point, if PMI was running $180 a month, your payment drops by that amount for the remaining 25 years. That's a $54,000 swing over the life of the loan, triggered by one row in a table. Find that row on your own schedule and mark it on your calendar, and read our PMI removal guide for the request letters and appraisal strategy. Extra principal payments pull that row forward — another reason the early-payment math in the table above compounds.
Amortization and Your Taxes: What's Deductible
One more reason to understand your schedule: the interest column is what feeds the mortgage interest deduction. For most homeowners, the interest portion of their payment is deductible on federal taxes — subject to the standard deduction, which in 2026 sits at roughly $14,600 for single filers and $29,200 for married couples filing jointly. In the early years of a 6.625% loan, you'll almost certainly clear the standard deduction threshold; by year 20, with interest down to $12,807 on the $350,000 example, you may not.
Two practical points. First, if you itemize, keep your annual mortgage interest statement (Form 1098) — it's your official record of the interest column. Second, the deduction changes the effective cost of your interest but not the mechanics of your schedule: prepaying still saves you the interest, and you lose the deduction on the interest you no longer pay. At a 24% marginal rate, every $1,000 of interest eliminated costs you about $240 of deduction — the net saving is $760, not $1,000. The deduction softens the pain of amortization; it doesn't change which payment strategy wins. For the full rules — including the $750,000 loan limit on deductible acquisition debt — our mortgage interest deduction guide covers the details.
Frequently Asked Questions
Why is most of my early mortgage payment interest?
Amortization calculates interest on the full remaining balance every month. Early on, that balance is at its largest, so the interest slice is largest too. On a $350,000 loan at 6.625%, your first payment is $1,932 interest and just $309 principal. The split flips only in year 21.
How much interest do you pay in the first 5 years of a 30-year mortgage?
On a $350,000 loan at 6.625%, you pay about $112,571 in interest over the first five years — 84% of everything you pay in that window. Only about $21,894 goes to principal. This is why the first years of a mortgage build very little equity.
When does principal become more than interest on a mortgage?
On a 30-year fixed mortgage, principal exceeds interest around year 21. At 6.625% on $350,000, the crossover happens in month 250. A 15-year loan crosses over in year 8, because the balance is being paid down much faster.
Is it better to pay extra on principal or invest the money?
Extra principal payments earn a guaranteed return equal to your mortgage rate — 6.625% in our example — with zero risk. If you're already maxing out tax-advantaged retirement accounts and your rate is above what a low-risk investment returns, prepaying is mathematically sound. If your rate is below 4%, investing usually wins.
Does an amortization schedule change if I refinance?
Yes. Refinancing restarts the clock with a new schedule based on the new balance, rate, and term. If you refi into another 30-year loan, you reset the interest front-loading — which is why many people refinance into a shorter term or keep paying the old amount. Run the scenarios in a refinance calculator first.
Can I get my amortization schedule from my lender?
Yes — your lender can provide an official amortization schedule, and your annual escrow statement shows year-end balances. You can also generate one yourself with a spreadsheet formula or any amortization calculator, and it will match within a few cents.
What happens to the amortization schedule if I make one extra payment a year?
One extra payment per year shortens a 30-year loan by roughly 5 to 6 years at today's rates and saves well over $100,000 in interest on a typical $350,000 loan. The earlier you start, the bigger the effect, because you're removing principal that would otherwise accrue interest for decades.
The Bottom Line on Amortization
Amortization isn't designed to punish you — it's the arithmetic of borrowing. Your first payments are mostly interest because your debt is biggest then. The practical takeaways are simple. Understand your schedule before you sign: know your crossover month, know your total interest, and know what 80% LTV looks like on the balance column. Then decide, deliberately, whether prepaying fits your plan — an extra $100 a month is worth $64,725 on today's rates.
Run your own loan through the mortgage calculator to see your payment, check what a shorter term does with our affordability calculator, and use the refinance calculator before you reset the clock. If you're ready to shop rates, get pre-approved with real numbers in hand.