Use the result for a focused comparison.
- See how a level payment is divided between interest and principal.
- Estimate the remaining scheduled balance after a chosen number of payments.
- Compare the early and later stages of a fixed-rate mortgage.
Formula and calculation method.
M = P × i ÷ [1 − (1 + i)⁻ⁿ]; balance after k payments = P(1+i)ᵏ − M[(1+i)ᵏ−1]÷iThe fixed payment is calculated first. The selected payment’s opening balance determines that month’s interest; the remainder of the payment reduces principal. The balance formula summarizes all scheduled payments through month k.
Follow the numbers in context.
$300,000 mortgage at 6% for 30 years; inspect payment 12
Working: The fixed payment is calculated over 360 months, then the first 12 payment periods are summarized.
Result: About $1,798.65 monthly; roughly $296,316 remains after payment 12.
Interpretation: Early payments contain more interest because the outstanding balance is still close to the original principal.
Read the estimate with its assumptions.
Amortization is the gradual repayment of principal through scheduled payments. With a conventional fixed payment, the interest share normally declines as the balance falls.
The displayed snapshot excludes taxes, insurance, mortgage insurance, fees, and any unscheduled payment activity.
A balance snapshot is especially useful when checking a statement or estimating equity, but it is not a property-value estimate. Equity also depends on the home’s current value and any other secured borrowing. When comparing two mortgages, inspect both the payment and how quickly principal falls; a lower payment can accompany a much longer repayment period.
What the model includes—and leaves out.
- Fixed rate and equal monthly principal-and-interest payments.
- Payments occur exactly once per month.
- No extra payments, skipped payments, fees, or rate resets.
- The selected payment is within the contractual term.
This is a mathematical schedule, not a lender statement. Mortgage conventions can differ by country, including compounding frequency, day-count rules, payment frequency, and terminology. Confirm the official amortization schedule supplied by the lender. The model is a generic monthly fixed-rate calculation current as of September 2026; it does not claim to reproduce Canadian semi-annual compounding, UK daily-interest servicing, adjustable-rate resets, or another jurisdiction-specific convention.
Unusual inputs need extra care.
Every payment reduces principal by an equal amount.
The remaining balance is constrained to zero after the last scheduled payment.
The calculator asks for a payment number no greater than the total number of payments.
Questions about this calculation.
Why is so much of an early mortgage payment interest?
Monthly interest is calculated on the outstanding balance. The balance is largest near the beginning, so the interest amount is also largest then.
Does this include property tax or insurance?
No. The schedule covers principal and interest only. Use the main Mortgage Calculator for a broader monthly estimate that includes entered tax and insurance.
Is this schedule valid for every country?
No. The formula models monthly compounding and monthly payments. Canadian, UK, and other mortgage conventions may use different rate or payment rules.