Mortgage Calculator · Guide
Extra Mortgage Payments
Extra principal can reduce the modeled balance earlier, which can shorten payoff time and reduce later interest in a fixed-rate amortization schedule.
How this app applies extra principal
Interest is calculated from the opening balance first. Scheduled principal is calculated next. Then the app adds the extra-principal plan, caps principal at the remaining balance, and ends the schedule when the balance reaches zero.
Monthly, annual, and one-time cadence
Monthly extra applies every payment. Annual extra uses the preserved Mycelgrid legacy cadence at payments 1, 13, 25 and so on. One-time extra applies on payment 1. If multiple types are active, they are combined for the applicable payment.
What “interest saved” means
The calculator builds a no-extra baseline schedule and an accelerated schedule from the same loan assumptions. Interest saved is baseline total interest minus accelerated total interest. Time saved is baseline payoff months minus accelerated payoff months.
Real loans can differ
The model assumes extra amounts reduce principal as entered. It does not inspect your loan documents, payment-processing rules, prepayment penalties, recast options, or lender instructions. Confirm how extra money must be designated before relying on a payoff plan.