Amortization Schedule Calculator

An amortization schedule is the month-by-month map of your mortgage: what each payment is, how much of it pays interest, how much pays down your balance, and exactly what you still owe after every payment.

Every fixed mortgage payment is split two ways:

• Interest — the lender’s charge on the balance you still owe that month.
• Principal — the part that actually reduces your loan.

Early on, the balance is large, so most of the payment is interest. As the balance shrinks, the same payment shifts toward principal — slowly at first, then faster. The schedule shows that shift payment by payment, all the way to a $0 balance. The calculator above builds the full schedule instantly, lets you open any year to see its twelve payments, and can compare up to three loans side by side.

More than most people expect: on a $400,000 loan at 6.5% for 30 years, the first payment is $2,528.27 — and about $2,166.67 of it is interest, with only $361.61 reducing your balance.

That is not a trick or a bank gimmick — it is simply 6.5% yearly interest charged on a $400,000 balance, divided into months. As the balance falls, the split improves every single month:

The calculator marks the exact month your payments become majority-principal — a milestone worth watching, because every extra dollar you pay before that point does outsized work.

Every extra dollar goes straight at your balance, which shrinks the interest charged on every later month — on a $400,000 loan at 6.5%, just $200 extra a month pays the loan off about 5 years 7 months early and avoids roughly $111,900 of interest.

The calculator models three kinds of extra payments, alone or together:

• Monthly — the steady habit; the most powerful per dollar because it starts working immediately.
• Annual — a tax-refund-style lump once a year.
• One-time — a single lump at any payment you choose.

Two honest cautions. First, extra payments only work if your servicer applies them to principal — say “apply to principal” explicitly, or the money can sit as a prepaid regular payment and save you nothing. Second, money paid into the house is hard to get back out — fund your emergency account first.

On total interest, dramatically — on $400,000, a 15-year at 5.875% costs about $202,700 in interest versus about $510,200 for a 30-year at 6.5%. The catch is the payment: $3,348.47 versus $2,528.27, roughly $820 more every month, mandatory.

A middle path many people like: take the 30-year for safety, then pay it like a 15-year. You keep most of the interest savings and the right to fall back to the smaller required payment in a hard month. The calculator has a one-click switch for exactly this — “Also pay the other loan’s payment” — so you can see what the discipline is worth on your own numbers. (Rates here are examples — confirm current quotes.)

It can be a smart move, but it does something different than most people expect: prepaying an ARM usually shows up as a lower future required payment rather than a shorter loan.

Here is why. At every adjustment, an ARM recalculates its payment from the balance you actually owe. Pay extra during the cheap fixed years and the balance at the first reset is smaller — so the recalculated payment is smaller too, and the total interest falls. If the check you keep writing stays comfortably above even the recalculated payment, the surplus keeps prepaying principal and you can still finish early — the calculator shows exactly which way your numbers break.

That makes the “write the 30-year-fixed check on the ARM” strategy a payment-shock cushion: you bank the discount years, and the reset hits a smaller balance. The calculator models this honestly — including the moment your ARM’s own rising payment overtakes the check you were writing, when the strategy quietly stops adding anything extra.

Every ARM contract contains caps — the most the rate can move at the first adjustment, at each later one, and over the life of the loan. “Worst case” is simply your rate riding those caps to the ceiling: not a prediction, but the highest your contract allows the rate to go.

For example, a 5/6 ARM starting at 6.5% with 2/1/5 caps can reach 8.5% at year five, then step up to a lifetime ceiling of 11.5% — and the calculator shows the exact payment at every step.

The planning rule we suggest: test your budget against the worst-case payment, then celebrate anything better. If the ceiling payment would break you, the ARM’s discount is rented, not owned — and refinancing later is a bet on rates, not a plan. The calculator lets you flip between worst case, rate-stays-put, and your own guess, so you can see all three futures before you commit. Caps vary by lender — check your Loan Estimate.

Two different rules, two different dates — and both measure against your home’s original value — on a purchase, the lower of your purchase price and the appraisal at closing, not what the home is worth today: you can ask for cancellation when your balance reaches 80% of that original value — and extra payments get you there sooner — but automatic termination at 78% follows the original payment schedule, no matter how fast you actually prepay.

That split comes from the federal Homeowners Protection Act, and it surprises people constantly:

• 80% of original value — your request. Based on your actual balance, so prepaying moves this date up. You typically need a good payment history, and you have to ask — it rarely happens by itself the day you qualify.
• 78% of original value — automatic. Based on the amortization schedule as originally written, so extra payments do not accelerate this one — and you need to be current on your payments when the date arrives.

Enter the home’s original value in the calculator’s options and it marks both dates on your schedule. (Appreciation can open other doors — some servicers cancel based on current value with a new appraisal — but that is their call, not the HPA rules shown here. This applies to conventional PMI; FHA mortgage insurance follows different rules.)

On a fixed-rate loan, no — the required payment never changes; extra money shortens the loan instead. On an ARM, yes — at the next adjustment the payment is recalculated from your smaller balance.

This is one of the most misunderstood facts in home finance, and it cuts both ways:

• Fixed loan: pay $200 extra for years and your bill still reads the same number — but the loan ends years early and the interest you never pay can run six figures.
• ARM: the same habit typically shows up as a smaller required payment at each reset — relief you can feel — while the payoff date usually stays put (keep paying far above the recalculated payment and it can still move up).

Neither is better in the abstract; they are just different shapes of the same win. If you want a lower payment on a fixed loan, the usual tools are a recast (a lump sum plus a servicer fee to re-spread the balance) or a refinance — both worth pricing out with a human before you commit.

Yes — that is the whole point of this tool. Open any year in the table to see all twelve payments: the date, the payment, the interest, the principal, any extra, and the exact balance you’d still owe.

Beyond the table, you can:

• Drag the marker on the balance chart to freeze any month — and read what you’d owe, the equity you’d have, the interest paid so far, and that month’s check for every loan at once.
• Compare up to three loans — each one fixed or ARM, each with its own extras — on one shared timeline.
• Take it with you — download the full month-by-month schedule as a spreadsheet-ready CSV, a summary PDF, or print it.

Everything here is principal and interest only — taxes, insurance, and mortgage-insurance dollars ride on top of these numbers, and your Loan Estimate is always the final word.