Mortgage Penalty Calculator for Prepayment Cost Analysis

The mortgage penalty calculator estimates the fee a lender may charge when you pay a closed mortgage down early. It is most common on Canadian closed terms and on some U.S. loans with a stated prepayment charge. Enter the current balance, note rate, market rate, the amount you plan to prepay, the penalty method, and—for interest-rate differential—the remaining penalty months. Remaining term in years is a reference field and is not used in the dollar math. The prepaid amount is capped at the current balance so you cannot penalize more principal than you owe. Two methods are supported. Three months of interest is prepaid × (note rate / 12) × 3, regardless of the penalty-period input. Interest-rate differential (IRD) is prepaid × max(0, note rate − market rate) × (penalty months / 12). If the market rate is at or above the note rate, IRD is zero under this simple posted-rate version. Net prepayment is the extra principal minus the estimated penalty—the amount that actually reaches the balance after the fee. Penalty method rate shows the rate used in the formula: the full note rate for the three-month method, or the rate gap for IRD. Use the mortgage penalty calculator before breaking a term to refinance, before selling, and before making a lump-sum payment larger than the annual prepayment privilege. Many notes charge the greater of three months’ interest and IRD; run both methods and compare. Posted-rate IRD can differ from discounted-rate IRD in a contract. Some lenders apply IRD to the remaining term in months, others to a different period. Always read the mortgage charge clause. The estimate ignores discharge fees, reinvestment fees, and lost-rate holdbacks. U.S. conventional loans often have no penalty after a lock-in period; in that case the result is a hypothetical. Recalculate with the servicer’s market rate definition, and treat the output as a planning number rather than a payout statement.