See your loan’s payment schedule, interest and savings from extra payments. For yearly mortgage overpayments starting later, use the Mortgage Payoff Calculator.
“Annual contract interest rate (%)” excludes fees. A fee-inclusive APR can give the wrong payment schedule. Interest rate versus APR
Advanced options
Balance over time
Payment mix snapshots
| Date | Payment | Interest | Principal | Balance |
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How to use this calculator
Need yearly extra payments that begin later? For a current mortgage, use the Mortgage Payoff Calculator. Enter “Extra principal per year (USD/year)”, then set “When do recurring extra payments start?” and “Month for yearly extra payment” in “Advanced options”. That tool works from your current balance; this page retains a loan schedule with your chosen first payment date.
- Enter the loan amount (principal), which is the amount you borrowed. Currency fields accept plain digits, conventional three-digit comma grouping, or a leading dollar sign, such as 250000, 250,000, or $250,000.
- In "Annual contract interest rate (%)", enter the loan’s contract interest rate, not a fee-inclusive disclosure APR. This schedule divides the entered interest rate by the number of payments per year and handles your entered fees separately.
- Enter the loan term in years (how long the loan would last with only the required payments).
- Pick a payment frequency: Monthly (12 per year), Biweekly (26 per year), or Weekly (52 per year).
- Set the first payment date, or leave it blank to start one period from today (based on the frequency).
- Optional: Open Advanced options to add an extra payment each period, a one-time lump sum (and its date), upfront fees (and whether fees are added to the loan), or a balloon balance and balloon date.
- Click Calculate to see the required payment (without extras), payoff date, totals, and the full amortization schedule with dates.
- Use the comparison outputs (time saved and interest saved vs base plan) to understand how your extra payments or balloon change the total cost.
Methodology
Definitions: Principal is the amount borrowed at the start. Interest is the cost of borrowing. Balance is what you still owe before a payment. Term is how long the loan lasts in years. Payment frequency is how often you pay (monthly, biweekly, weekly). Amortization means each payment includes some interest and some principal, so the balance goes down over time. [1]
Step 1: Set payments per year based on frequency: monthly = 12, biweekly = 26, weekly = 52. Compute the periodic interest rate as rate per period = (contract annual interest rate as a percent / 100) / payments per year.
Step 2: Set the starting balance. If you choose to add upfront fees to the loan, starting balance = loan amount + fees. If not, starting balance = loan amount, and fees are tracked only as a separate cost.
Step 3 (base plan required payment): Let requested payments = loan term in years * payments per year. With "Round interest to cents each payment," all balances, interest, principal, and payments are whole cents. The calculator searches cents and chooses the lowest required payment that reaches a zero balance within the requested term; one cent less must not finish that term. With carry-decimals mode, it uses the standard fixed-payment formula. The chosen required payment is shown as "Required payment (without extras)".
Step 4 (build the schedule, one payment at a time): For each payment date in RoundEach mode, rounded interest cents = round(current balance cents * rate per period), actual payment cents are capped at balance plus interest, principal cents = payment cents - interest cents, and new balance cents = old balance cents - principal cents. Every completed row must satisfy payment = interest + principal and must strictly reduce the balance. Recurring and dated extra payments are included in that period actual payment without allowing the balance to fall below zero.
Step 5 (rounding choice): If "Round interest to cents each payment" is selected, each schedule row is computed in integer cents before the next balance is calculated. If the other rounding option is selected, the calculator keeps full precision internally and rounds only displayed values. Different lender rounding conventions can still produce small differences.
Step 6 (last payment cap): If extras would make the balance go below 0, the last payment is reduced so the ending balance becomes exactly 0. Payoff date is the date of that final payment. Number of payments is how many payment rows were needed.
Step 7 (balloon option): If a balloon date is set, the schedule stops on the first scheduled payment date that is on or after the balloon date. The remaining balance at that stop point is reported as the balloon balance due. If a balloon balance amount is also entered, it is treated as a target and must not be greater than the starting balance; the schedule stops when the computed balance is at or below the target (within normal cent rounding), and that remaining amount is reported as due.
Step 8 (totals and comparison): Total interest paid is the sum of all per-payment interest amounts in the schedule. Total principal paid is the sum of all principal reductions (including extras) and does not include any balloon balance left unpaid. Total fees paid equals the upfront fees entered. Interest saved vs base plan and time saved vs base plan are computed by running a base schedule with the same loan, rate, term, frequency, and first payment date, but with no extras, no balloon, and no fees added to the loan (fees tracked separately), then subtracting your scenario results from the base results.
Safety rules: Currency fields accept plain digits, conventional three-digit comma grouping, or a leading dollar sign and reject malformed grouping or more than two decimal places. Inputs must be non-negative where appropriate, term and loan amount must be greater than 0, a lump sum date is required if the lump sum amount is greater than 0, balloon date cannot be before the first payment date, and the schedule stops with an error if it would exceed 10000 payments to avoid infinite loops.