Does this calculator assume my extra payment goes directly to principal?

Yes. It assumes your lender applies extra payments to principal after covering the scheduled interest and principal for that month. Always confirm your lender’s prepayment policy and specify that extras should go toward principal.

Can I model occasional lump-sum payments?

This version focuses on a fixed extra monthly payment. You can approximate the effect of a lump sum by reducing the loan amount or by treating the lump-sum effect as an equivalent monthly extra for comparison.

Does this include taxes, insurance, or PMI?

No. The calculator works with principal and interest only. Add escrowed costs separately when building your full monthly housing or loan budget.

finance calculator

Loan Payoff with Extra Payment

See how adding a fixed extra monthly payment accelerates payoff and reduces total interest compared to the standard schedule.

Results

Base monthly payment (P&I): $1,799
Monthly payment with extra: $1,999
Payoff months (standard): 360.00
Payoff months (with extra): 279.00
Months saved: 81.00
Total interest (standard): $347,515
Total interest (with extra): $256,341
Interest saved: $91,173

How to use this calculator

Enter your loan amount (the current or starting principal balance), interest rate (APR), and remaining term in years.
Enter the fixed extra monthly payment you plan to add on top of the standard principal-and-interest payment.
We calculate the base monthly payment and simulate a standard payoff schedule.
We simulate a second schedule where the extra payment is added each month and applied directly to principal.
Review the new payoff time with extra payments, the months saved, and how much interest you would avoid paying.
Experiment with different extra payment amounts to find a target that balances faster payoff with an affordable monthly budget.

Inputs explained

Loan amount: The principal balance of your loan. For a mortgage, you can use either the original loan amount or the current remaining balance if you want to model from today forward.
Interest rate (APR %): The annual percentage rate on your loan. This should be the nominal interest rate, not including escrowed taxes or insurance.
Term (years): The total length of the loan in years. For an in-progress loan, you can approximate the remaining term to see how extra payments affect payoff from this point forward.
Extra monthly payment: The additional amount you plan to pay toward principal each month beyond the required principal-and-interest payment. The calculator assumes you make this extra payment consistently every month.

How it works

We first compute the standard fixed monthly principal-and-interest payment using the loan amount, interest rate, and term with a standard amortization formula.

Using that base payment, we simulate a typical amortization schedule month by month to determine how long the loan would take to pay off and how much total interest you would pay with no extra payments.

We then add your chosen extra monthly payment to the base payment and re-run the month-by-month simulation, applying the extra amount directly to principal each month.

From the extra-payment simulation, we compute the new payoff month and total interest paid with the extra amount.

We compare the standard and extra scenarios to calculate months saved (how much sooner the loan pays off) and interest saved (how much less interest you pay overall).

Formula

Base payment (P) for a fixed-rate loan: P = r × L ÷ (1 − (1 + r)^(-n)), where L is loan amount, r is monthly interest rate (APR ÷ 12), and n is total number of months.\nWe then simulate month by month applying P (and P + extra) to interest and principal to determine payoff time and total interest in both scenarios.

When to use it

Planning an acceleration strategy for mortgages, auto loans, or other fixed-rate amortizing debt.
Evaluating how redirecting a small amount of extra cash each month toward debt payoff can shorten your payoff horizon.
Comparing different extra payment levels (for example, $50 vs $200 per month) to see which delivers the most meaningful time and interest savings.
Using the results as a talking point when deciding between investing extra cash or paying down debt faster.

Tips & cautions

Even relatively small extra payments can cut years off a long-term mortgage and significantly reduce interest—test multiple scenarios to see the impact.
Check your loan documents for prepayment penalties or restrictions; factor any fees into your decision-making separately, as they are not modeled here.
If your income is variable, consider setting a conservative extra payment in the calculator, then using windfalls or bonuses for occasional lump-sum payments.
Revisit your extra payment plan periodically as your budget, interest rates, or financial goals shift.
Assumes a fixed-rate, fully amortizing loan and a constant extra payment amount each month.
Does not model adjustable-rate loans, interest-only periods, balloon payments, or changing payment schedules.
Ignores escrowed costs such as property taxes, insurance, and HOA dues, as well as fees and prepayment penalties.
Assumes payments are made exactly on schedule; early or late payments, skipped payments, and partial prepayments are not explicitly modeled.

Worked examples

30-year mortgage with $200 extra per month

Loan amount = $300,000, APR = 6%, term = 30 years, extra payment = $200.
The calculator computes the base payment and standard payoff timeline, then simulates the payoff with the extra $200 each month.
Interpretation: you may see that the loan pays off several years early and that you save tens of thousands of dollars in interest compared to the standard schedule.

Testing smaller extra payments

Run the calculator with extra payment = $50 and note the months and interest saved.
Increase the extra payment to $100 and run it again.
Compare the results to see how doubling your extra payment affects payoff time and total interest savings.

Deep dive

See how an extra monthly payment accelerates loan payoff and reduces total interest with this extra payment calculator.

Enter your loan amount, interest rate, term, and extra monthly payment to compare standard payoff time, interest paid, and months saved.

Ideal for homeowners and borrowers who want to understand the impact of rounding up payments or adding a fixed amount toward principal every month.

FAQs

Does this calculator assume my extra payment goes directly to principal?: Yes. It assumes your lender applies extra payments to principal after covering the scheduled interest and principal for that month. Always confirm your lender’s prepayment policy and specify that extras should go toward principal.
Can I model occasional lump-sum payments?: This version focuses on a fixed extra monthly payment. You can approximate the effect of a lump sum by reducing the loan amount or by treating the lump-sum effect as an equivalent monthly extra for comparison.
Does this include taxes, insurance, or PMI?: No. The calculator works with principal and interest only. Add escrowed costs separately when building your full monthly housing or loan budget.

Related calculators

finance

Prepayment Mortgage Reduction

See how extra monthly or biweekly payments shorten mortgage payoff and cut interest compared to the standard schedule.

finance

Biweekly vs Monthly Mortgage

Compare monthly versus biweekly payments to see payoff time, interest paid, and savings from the accelerated schedule.

This loan payoff with extra payment calculator is an educational tool based on a simplified fixed-rate amortization model. It does not account for adjustable rates, penalties, escrowed costs, fees, or taxes and is not a lender quote or personalized financial advice. Always review your loan documents and consult a qualified professional before committing to major payment changes or refinancing decisions.