Mortgage Amortization Calculator

What an amortization schedule shows you

A payment calculator tells you what you owe each month. An amortization schedule tells you where that money actually goes.

It is a row for every single payment across the whole loan. For each one you get the date, the payment amount, how much of it was interest, how much of it reduced your balance, your running total of interest, and what is left owing afterwards.

On a thirty year mortgage that is 360 rows. Sounds like a lot to read, and it is, which is why almost nobody reads it. That is a shame, because a handful of those rows carry information that is genuinely useful and that you cannot get any other way. Two of them are covered further down: the month your payment starts doing more good than harm, and the month your mortgage insurance is scheduled to come off.

Filling in the five fields

1. Loan Amount. What you are borrowing, after the down payment has come off. Not the purchase price.
2. Interest Rate. Your annual rate as a percentage. This is the interest rate, not the APR.
3. Loan Term. Years to repay. Thirty and fifteen are the common ones.
4. First Payment Date. Starts on today's date, and you can set it to whenever your first payment is actually due. This drives the whole date column and the payoff date.
5. Amortization Schedule. Show by month for every payment, or show by year for a summary row per year. Yearly is the better place to start.

Press Calculate and you get a summary block first, with the payment, the payoff date and the totals, followed by the schedule itself.

How a single row is built

The whole schedule comes from three lines of arithmetic repeated over and over. Once you have seen them the table stops looking like a spreadsheet and starts looking like a story.

Before any of it, the calculator works out the fixed monthly payment using the standard amortising formula:

M = L × i ÷ (1 - (1 + i)^-n)

where L is the loan, i is your annual rate divided by 12 and by 100, and n is the term in months. That payment then stays the same for every row.

Now for each month, in order:

1. Interest = current balance × i. Interest is always charged on what you currently owe, which is why it shrinks as the loan does.
2. Principal = payment - interest. Whatever the interest does not swallow goes at the balance.
3. New balance = old balance - principal. Then the next row starts from there.

That is it. Every row in the table is those three lines, run again with the balance from the row above. The reason the schedule looks so lopsided at the start is not a rule anybody wrote down. It falls straight out of step one, because early on the balance is nearly the whole loan.

The final row gets one small adjustment. If the last principal payment would be larger than the tiny balance still standing, the calculator trims it to exactly the balance, so the loan closes at zero rather than overshooting into negative.

Watching a 300,000 loan from month one

Take 300,000 at 6 percent over 30 years. The monthly payment works out to 1,798.65, and it never changes.

Payment 1. Interest is 300,000 × 0.005 = 1,500.00. Principal is 1,798.65 minus 1,500.00 = 298.65. New balance: 299,701.35.

So you have handed over 1,798.65 and you own 298.65 more of your house. Just under 17 percent of the payment did anything for you.

After a year. Twelve payments, 21,583.80 out of your pocket. Your balance has fallen to 296,315.96, which means 3,684.04 of principal repaid and 17,899.78 gone in interest.

Payment 360. Interest is 8.95. Principal is 1,789.70. Balance zero. Identical payment, almost entirely principal.

Across the whole thing you pay 347,514.57 in interest on a 300,000 loan. And here is the comparison that lands hardest: in year one you repaid 3,684 of principal. In year thirty you repay 20,898. Same payment, nearly six times the effect.

The month the payment finally tips over

Somewhere in every amortising loan there is a month where the principal portion first grows larger than the interest portion. Before it, most of your payment is rent on the money. After it, most of it is buying the house.

On our 300,000 at 6 percent over 30 years, that month is payment number 223. Which is eighteen years and seven months in.

Read that again, because it is not intuitive. On a thirty year loan you spend more than eighteen years paying mostly interest. The balance at that point is still 178,084, so after almost nineteen years of payments you have cleared about 41 percent of the loan.

The crossover is not printed as a label anywhere in the table, but it is easy to spot. Scroll the monthly schedule and look for the first row where the Principal column overtakes the Interest column. On shorter terms it arrives much earlier, and on a fifteen year loan it is there almost from the start, which is a large part of why shorter terms cost so much less overall.

Finding the month your mortgage insurance ends

This is the most valuable thing in the table for anyone who put down less than 20 percent, and it is worth being precise about, because the rules are statutory rather than a matter of lender goodwill.

In the US, the Homeowners Protection Act gives you two separate rights on private mortgage insurance. You can request cancellation once the balance reaches 80 percent of the property's original value. And the servicer must automatically terminate it when the balance is first scheduled to reach 78 percent of original value, provided you are current on payments.

The word doing the heavy lifting there is scheduled. Automatic termination runs off the initial amortization schedule, which is exactly the table this tool prints. So you can find your own date.

Take a 400,000 home with 10 percent down. The loan is 360,000, and at 6 percent over 30 years the payment is 2,158.38. Now:

• 80 percent of the original 400,000 value is 320,000. The schedule crosses that at payment 89, about seven and a half years in. That is the earliest you can ask.
• 78 percent is 312,000. The schedule crosses that at payment 103, roughly eight and a half years in. That is when it should come off by itself.

Fourteen payments sit between those two dates. On a policy costing, say, 150 a month, asking rather than waiting is worth a couple of thousand.

Two details that matter. Original value means the lower of the contract sales price or the appraised value at the time you bought, and if you have refinanced it means the appraised value at the refinance. And extra principal payments genuinely bring the cancellation date forward, because the 80 percent request right can be based on actual payments rather than the schedule.

There is also a third route worth knowing about. Even if the balance has not reached 78 percent, mortgage insurance generally has to end at the midpoint of the amortization period if you are current, which on a thirty year loan means after fifteen years.

Checking the schedule against your statement

If you already have a mortgage, run your original loan amount, rate and term through here and compare the row for your current month against your latest statement.

They should be very close. If they are not, the usual explanations are ordinary rather than sinister. Your statement includes escrow for taxes and insurance, so the total will be higher. You may have paid a little extra at some point, which pulls the balance ahead of the schedule. Or your loan started with a stub period between closing and the first full payment, which shifts everything slightly.

What you are really looking for is the interest column. If the interest your servicer charged is meaningfully above what the schedule says for that balance, that is a question worth asking them.

The date column and how it steps

The First Payment Date field is what turns an abstract list of 360 rows into something you can plan around. Set it to the date your first payment is actually due, and every row afterwards steps forward exactly one calendar month.

That gives you the payoff date in the summary block, which is a genuinely useful number to have. It is also what makes the mortgage insurance dates above concrete rather than theoretical, since you get an actual month and year rather than a payment number.

Dates in the middle of a month step cleanly. If your payment falls on the 1st or the 15th, every row will land on the 1st or the 15th all the way through.

Where the totals come from

The summary block reports total interest by adding up the interest column of the schedule itself, row by row, rather than by multiplying the payment out and subtracting the loan.

That is the more careful of the two methods and it is worth knowing which one you are looking at. Because the last row is trimmed to close the balance at exactly zero, a schedule total accounts for that final adjustment where a simple multiplication does not. On our 300,000 example both approaches land on 347,514.57, but on loans where the final payment needs a larger trim the schedule figure is the one to trust.

Everything inside the schedule is calculated at full precision and rounded only when it is printed. So if you add the printed Principal column by hand you may land a cent or two away from the loan amount. Your lender has the same issue in reverse, since they round each payment to the cent as they collect it, and the accumulated difference usually gets absorbed into a slightly different final payment.

Monthly view or yearly view

Start with the yearly view. Thirty rows instead of 360, and it answers most questions faster: how much of this year went to interest, where the balance stands at each anniversary, and when the curve finally starts bending.

Switch to monthly when you want a specific row. Finding your mortgage insurance month, locating the crossover payment, or checking a particular statement all need the detail. The monthly table also carries a running total of interest paid, which is the column people tend to stare at longest.

One habit worth building. Run the yearly view once, note the balance at year five and year ten, then compare those against what the house might reasonably be worth by then. That gap is your equity, and it is a more honest picture of where you stand than the payment figure on its own.

Questions people ask

What does amortization actually mean?

It is the process of clearing a debt through regular equal payments, where each payment covers the interest accrued since the last one and puts whatever is left toward the balance. The schedule is simply that process written out in full.

Why is nearly all of my early payment interest?

Because interest is charged on the balance you currently owe, and at the start you owe almost the whole loan. On a 300,000 loan at 6 percent, the first payment is 1,500 interest and 298.65 principal.

When does more of my payment go to principal than interest?

On a 30 year loan at 6 percent it happens at payment 223, around eighteen and a half years in. Shorter terms reach it far sooner, and on a 15 year loan the principal portion is larger almost immediately.

Can I use this to work out when my PMI comes off?

Yes, and that is one of the best uses for it. Find the row where the balance first drops to 78 percent of the home's original value, which is the point of automatic termination. The 80 percent row is when you can request cancellation yourself, and it usually arrives about a year earlier.

Does this account for extra payments?

The schedule is built on the scheduled payment, so it shows the path your loan takes if you pay exactly what is due each month. The mortgage overpayment and loan payoff calculators are built for modelling additional payments.

Why does my lender's statement not match this exactly?

Usually escrow. Your statement bundles property tax and insurance into the total, while this schedule covers only principal and interest. Extra payments you have made, or a stub period at the start of the loan, will also shift things.

What should I put as the first payment date?

The date your first full payment is due, which is often the first of the month after closing rather than the closing date itself. It sets the whole date column and the payoff date.

Is the total interest figure the payment times the term?

It is the sum of the interest column from the schedule, which accounts for the trimmed final payment. On most loans the two methods agree to the cent, and where they differ the schedule total is the more accurate one.

References

The payment formula and the row by row method are the standard actuarial amortisation approach, under which the unpaid balance is increased each period by the finance charge earned and decreased by the payment made, as set out in Regulation Z. The mortgage insurance cancellation and termination thresholds, the definition of original value, and the midpoint termination rule come from the Homeowners Protection Act of 1998 and the Consumer Financial Protection Bureau's guidance on it.

1. Consumer Financial Protection Bureau (CFPB), Regulation Z, Appendix J to Part 1026: Annual Percentage Rate Computations for Closed-End Credit Transactions. https://www.consumerfinance.gov/rules-policy/regulations/1026/j/
2. Consumer Financial Protection Bureau (CFPB), When Can I Remove Private Mortgage Insurance (PMI) From My Loan? https://www.consumerfinance.gov/ask-cfpb/when-can-i-remove-private-mortgage-insurance-pmi-from-my-loan-en-202/
3. Consumer Financial Protection Bureau (CFPB), Compliance Bulletin 2015-03: Private Mortgage Insurance Cancellation and Termination, 4 August 2015. https://files.consumerfinance.gov/f/201508_cfpb_compliance-bulletin_private-mortgage-insurance-cancellation-and-termination.pdf
4. Board of Governors of the Federal Reserve System, Background and Summary of the Homeowners Protection Act. https://www.federalreserve.gov/frrs/regulations/background-and-summary-of-the-homeowners-protection-act.htm
5. Consumer Financial Protection Bureau (CFPB), What is PITI? https://www.consumerfinance.gov/ask-cfpb/what-is-piti-en-152/