Extra Payment Calculator
See interest and time saved by paying extra.
Results update as you type.
How it works
Paying a little extra on a loan each month can save a surprising amount of interest and years of payments, and this calculator shows exactly how much. You enter the loan balance, interest rate, current monthly payment, and the extra amount you would add each month, and it returns the interest saved, the time saved, and the new payoff time. It works by computing the payoff time and total interest at your current payment, then recomputing with the higher payment, and reporting the differences. The reason extra payments are so powerful is that once your regular payment has covered the month's interest, every additional dollar goes straight to principal, reducing the balance on which all future interest is charged. This creates a compounding effect: a smaller balance means less interest next month, so more of every future payment attacks principal too. On a long mortgage, even a modest extra payment can cut years off the term and save tens of thousands in interest. The savings grow with the size of the extra payment, the interest rate, and the remaining term. This is one of the most effective and accessible ways to save money and become debt-free faster, requiring no refinancing. Make sure your lender applies extra payments to principal and check for prepayment penalties, which are rare but exist on some loans. Enter your loan details and extra payment to see your savings.
Compare payoff time and interest at the base vs. increased payment
The calculator finds the payoff time and total interest for your current payment, then again with the extra amount added, using the amortization payoff formula each time. The interest saved and months saved are the differences between the two scenarios. Every extra dollar attacks principal, so it compounds into large savings.
Source:Loan amortization
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter loan balance, interest rate, current monthly payment and extra monthly payment.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Interest saved updates instantly as you type — no button to press.
Frequently asked questions
How do extra payments save money?
Once your regular payment covers the month's interest, any extra amount goes entirely to principal, lowering the balance that future interest is charged on. This compounds: a smaller balance means less interest each month, so more of every payment reduces principal. Over time this cuts both total interest and the payoff period substantially.
How much can an extra payment save?
It depends on the loan size, rate, term, and how much extra you pay, but on a long mortgage even a modest extra monthly amount can shave years off the loan and save tens of thousands in interest. The calculator shows the exact interest and time saved for your specific loan and extra payment.
Is it better to pay extra monthly or make a lump sum?
Both help, but consistent extra monthly payments start reducing principal immediately and build a lasting habit. A lump sum reduces the balance all at once. Either way, the key is that the money is applied to principal. Paying extra earlier in the loan saves more, since interest is front-loaded on amortizing loans.
Should I make sure the extra goes to principal?
Yes. Confirm with your lender that additional payments are applied to the principal balance, not held toward the next payment or future interest. Some require you to specify this. Applying extra to principal is what generates the interest savings, so verify how your lender handles it to get the full benefit.
Are there downsides to paying extra?
The main considerations are ensuring you have an emergency fund first, checking for rare prepayment penalties, and weighing whether the money could earn more invested elsewhere, especially if your loan rate is low. For high-interest debt, paying extra is usually one of the best guaranteed returns available, since it saves that interest rate risk-free.