Reading an amortization schedule
An amortization schedule is the month-by-month arithmetic behind a fixed payment. Each row does the same two things: interest is charged on the balance you still owe, and whatever is left of the payment reduces that balance. Because the balance shrinks, the interest charge shrinks with it, so the share going to principal grows every single month while the payment itself never moves.
The consequence is front-loading, and it is steeper than most people expect. On a 30-year loan the first payment is typically 75–80% interest. You do not reach a 50/50 split until roughly the eighteenth year, and the final payments are almost entirely principal. This is not a fee structure — it is just what charging interest on a declining balance produces. Nobody is front-loading the interest deliberately.
Two practical readings follow. First, extra payments are worth most at the start, because every dollar removed from the balance early avoids interest on that dollar for the entire remaining term; the same dollar paid in year 25 avoids almost nothing. Second, the schedule tells you your real equity position at any date — useful before selling, refinancing, or working out when you will cross the 20% threshold where private mortgage insurance can be cancelled.