Generate a full mortgage amortization schedule showing principal vs interest for every payment. See how extra payments save thousands in interest on any 30-year mortgage.
Full schedule with extra payment savings
| Year | Payment | Principal | Interest | Balance |
|---|
A mortgage amortization calculator reveals something most homeowners find surprising: on a $300,000 loan at 6.5%, your very first monthly payment of $1,896 sends roughly $1,625 to the lender as interest and only $271 toward actually paying down the principal. That ratio gradually flips over 30 years, but the early years are overwhelmingly interest-heavy. Viewing a full amortization schedule — every principal vs interest split, year by year — makes this stark reality visible and helps you plan extra payments strategically.
The loan payoff power of small extra payments is dramatic. On that same $300,000 / 6.5% / 30-year loan, paying just $200 extra each month cuts roughly 5.5 years off the loan term and saves over $60,000 in total interest. A one-time $5,000 lump sum early in the loan life saves far more than the same $5,000 paid in year 20, because interest compounds forward. Homeowners who refinance often use an amortization schedule to see exactly how many years of interest they are resetting — information that dramatically changes the math on whether refinancing makes sense.
In month one of a typical 30-year mortgage, 85%+ of your payment is pure interest. It takes about 18 years before your principal payment finally exceeds your interest payment each month.
Adding $100/month to a $250,000 loan at 6.5% saves roughly $33,000 in interest and cuts 3+ years off the term — without refinancing or changing your loan.
A 15-year mortgage at 6.0% on $300,000 costs $2,532/month but saves over $130,000 in interest vs a 30-year at 6.5%. Use the schedule to see exactly where that savings comes from.
If you refinance in year 5 of a 30-year loan, you reset to year 1 amortization on the new loan — meaning interest-heavy payments start again. The schedule helps you weigh that cost against rate savings.
An amortization schedule is the payment formula applied repeatedly, one row per period, tracking how the balance falls. Each row does the same three things: charge interest on what is currently owed, treat the remainder of the payment as principal, and carry the reduced balance forward. Because the payment is level while the balance shrinks, the interest charge falls every month and the principal portion grows by exactly the same amount — the split moves smoothly rather than in steps. Reading a schedule is the clearest way to see why loan term affects total interest so much more than intuition suggests.
Interest_t = Balance_(t−1) × iPrincipal_t = M − Interest_tBalance_t = Balance_(t−1) − Principal_twhere:
Assumptions: Assumes payments arrive exactly on schedule and interest accrues monthly on the outstanding balance. Daily-accrual loans differ slightly, and an extra payment changes every row after it.
Take the $400,000 30-year loan at 6.5% with its $2,528.27 payment and build the schedule by hand.
ResultMonth 1: $2,166.67 interest / $361.60 principal — 86% of the payment is interest
After a full year of payments totalling $30,339 the balance has fallen only about $4,471. Adding $200 a month from the start retires this loan roughly five years early and saves over $100,000 in interest, because every extra dollar removes all future interest on itself.