Mortgage Amortization Schedule Calculator

In the early years of a fixed mortgage, most of each payment goes to interest. On a $300,000 / 6.5% / 30-year loan, the first payment is ~81% interest and ~19% principal; the ratio flips only around year 21. Every payment afterward is mostly principal.

Loan amount

Interest rate (APR)

Loan term

Fill in loan amount and APR to see the full schedule.

0 of 2 filled in.

How amortization works

Every month you pay a fixed amount on your mortgage, but the split between principal and interest changes with every payment. Early in the loan, almost all of your payment goes to interest. Late in the loan, almost all of it goes to principal.

That's amortization. The word comes from Latin ad mortem — "to the death." Each payment slightly kills off the loan balance.

The reason for the front-loaded interest: monthly interest is computed on the remaining balance. When the balance is near the original loan amount, the interest charge is near the maximum. As the balance shrinks, the interest charge shrinks with it, and more of your fixed monthly payment flows to principal.

On a 30-year $300,000 loan at 6.5%:

Month 1: $1,896 total payment = $1,625 interest + $271 principal
Month 180 (halfway through): ~$1,896 payment = $1,186 interest + $710 principal
Month 360: ~$1,896 payment = $10 interest + $1,886 principal

This is why mortgage payoff is slow at the start — and why every extra dollar of principal you pay in year 1 saves you far more than a dollar of principal paid in year 25.

Formula

The classic amortization formula:

monthly_payment = principal × (r × (1 + r)^n) / ((1 + r)^n − 1)

Where:

principal = original loan amount
r = monthly interest rate (APR ÷ 12)
n = total number of payments (years × 12)

For each month, the schedule computes:

interest_this_month  = current_balance × r
principal_this_month = monthly_payment − interest_this_month
new_balance          = current_balance − principal_this_month

This repeats for n months until the balance reaches zero.

Scenarios at a glance

Principal vs interest breakdown on a $300,000 / 6.5% / 30-year fixed mortgage (monthly payment $1,896):

Year	Principal paid that year	Interest paid that year	Remaining balance
1	~$3,300	~$19,450	$296,700
10	~$5,600	~$17,150	$254,000
20	~$10,800	~$11,950	$145,500
30	~$22,100	~$650	$0

Two extra principal payments of one month each year — about $317/month extra — cuts a 30-year loan to roughly 23 years and saves ~$90,000 in interest.

Worked example

Sarah takes out a $350,000 mortgage at 6.5% for 30 years. The calculator shows:

Monthly P&I: $2,212.24
Total interest over 30 years: $446,404 — more than the loan itself
Total paid: $796,404

Looking at the yearly schedule:

Year	Principal paid	Interest paid	Ending balance
1	$3,789	$22,758	$346,211
5	$4,916	$21,631	$327,211
10	$6,794	$19,753	$298,013
15	$9,390	$17,157	$253,700
20	$12,980	$13,567	$193,470
25	$17,942	$8,605	$110,223
30	$24,802	$1,745	$0

Notice the shift: in year 1, Sarah pays $22,758 in interest. In year 30, she pays $1,745 in interest. The monthly payment is the same throughout; what changes is where each dollar of that payment goes.

This asymmetry is the engine behind two common strategies:

Pay extra principal early. An extra $200/month in year 1 shaves 5+ years off the loan and saves ~$80,000 in interest. The same extra $200/month starting in year 20 saves only a few thousand.
Refinance early if rates drop. Rate reductions compound against your balance, which is highest in early years.

FAQ

What's the difference between APR and interest rate?

On the calculator, use your interest rate (the rate used to compute interest on the balance). APR includes points and some fees — it's used for comparison shopping, not for amortization math. Your Loan Estimate document shows both; the interest rate is the smaller number.

Does this include taxes and insurance?

No — P&I only. Your full monthly payment (PITI) is principal + interest + property taxes + homeowners insurance, and often HOA dues. The escrow portion varies by locality and is calculated separately.

What if I have an adjustable-rate mortgage (ARM)?

The schedule assumes a fixed interest rate for the entire term. ARMs have a fixed introductory period (typically 5, 7, or 10 years) then adjust. Use the calculator for the fixed period only; re-run it with the new rate after each adjustment.

How does this change with a biweekly payment schedule?

Biweekly means you pay half your monthly amount every two weeks — which adds up to 13 full monthly payments per year instead of 12. That extra payment per year reduces the principal faster, so the effective payoff is 4–5 years earlier on a 30-year loan. Our standard calculator models monthly payments; for biweekly, you'd divide the monthly by 2 and re-run with months × 2 as the number of payments (and with a slightly different rate calculation).

Do I pay interest on today's balance or yesterday's balance?

The balance at the start of the billing cycle. Because you pay monthly, the balance is locked in for the whole month; interest for the cycle is computed against that fixed balance.

Why is the first month's interest so high?

It's mathematical, not a trick. Your balance is at its peak the first month; monthly interest is balance × monthly rate, so it's also at its peak. Every subsequent month the balance is slightly lower, so the interest is slightly lower, and principal is slightly higher — all while the total payment stays constant.