Debt Payoff and Savings Calculator: Compare Your Goals

A debt payoff and savings calculator estimates how long it takes to repay a balance at a chosen monthly payment, and how much money you could accumulate by saving alongside that payment. Enter your debt balance, APR, monthly debt payment, monthly savings deposit, savings return, and time horizon to see the payoff time and estimated savings balance.

Formula

The payoff calculation uses a fixed monthly payment and a constant monthly interest rate. Its standard estimate is:

n = ceil(round(-ln(1 - r × B / M) / ln(1 + r), 6))

• n is the estimated number of monthly payments.
• r is the monthly debt interest rate, calculated as APR ÷ 1,200.
• B is the starting debt balance in dollars.
• M is the monthly debt payment in dollars.

This calculation requires the payment to exceed the interest charged in the first month. The savings estimate assumes equal deposits at the end of each month:

FV = D × ((1 + s)^t − 1) / s

• FV is the estimated savings balance in dollars.
• D is the monthly deposit in dollars.
• s is the monthly savings return, calculated as the annual return percentage ÷ 1,200.
• t is the number of monthly deposits, or years × 12.

Total savings deposits are D × t. For a zero savings return, the savings balance equals the total deposits; the displayed formula’s division by zero means that case should be read using this zero-return rule.

Worked Example

Using the calculator’s defaults: debt balance $10,000, debt APR 18%, debt payment $500 per month, savings deposit $200 per month, annual savings return 3%, and a three-year savings period.

1. Convert the debt APR to a monthly rate: r = 18 ÷ 1,200 = 0.015.
2. Calculate months to payoff: ceil(round(-ln(1 − 0.015 × 10,000 ÷ 500) ÷ ln(1.015), 6)), which is 24 months.
3. Convert the savings return: s = 3 ÷ 1,200 = 0.0025; the period is 3 × 12 = 36 months.
4. Calculate the savings balance: 200 × ((1.0025^36 − 1) ÷ 0.0025) = $7,563.51, rounded to cents.
5. Total deposits are $200 × 36 = $7,200.

The calculator’s first result is therefore 24 months to pay off the debt. At the same time, its projected savings balance after three years is $7,563.51, assuming the stated return and deposit timing.

Assumptions

• The debt APR and savings return stay fixed for the full calculation period.
• Debt payments and savings deposits occur monthly; deposits are assumed to arrive at the end of each month.
• Interest compounds monthly at the stated annual percentage divided by 12.
• Fees, taxes, insurance, and other costs or account features are not included.

When to Use the Calculator

Use it to compare the timing of a debt payoff with a separate savings goal under assumptions you can adjust. It can help answer questions such as whether a particular monthly payment would clear a balance within a chosen time, or how regular deposits might accumulate over the same period. It does not decide how much to direct to debt versus savings; that depends on personal circumstances the calculator does not model.

Try different payment amounts or savings deposits to see how the outputs change. For example, if the payment is close to the monthly interest charge, even a small difference can greatly change the estimated payoff time. A payment that does not cover monthly interest cannot repay the balance under this model, so the result is not computable.

How to Read the Results

Months to pay off is rounded up to a whole monthly payment period. It is a mathematical estimate, not a lender’s payoff quote. Real payment schedules may use daily interest, variable rates, payment dates, minimum-payment rules, or fees. Some final payments may be smaller than the regular payment; this simple formula estimates the number of equal payments rather than the exact final amount.

The savings balance includes the deposits and modeled growth. The difference between that balance and total deposits is estimated growth, not a guaranteed return. A savings account or investment may earn a different rate, and returns may vary. If the return is zero, the balance is just the sum of deposits.

Common Mistakes and Limits

• Entering an APR as a monthly rate: enter the annual percentage as a percentage, such as 18, not 1.5.
• Using a payment that is too small: if the payment is no greater than the first month’s interest, the debt does not decline under the fixed-payment model.
• Confusing deposits with growth: the savings balance includes the deposits themselves; compare it with total contributions to isolate modeled growth.
• Assuming dates do not matter: actual interest can depend on payment dates and how the account calculates interest. This tool uses monthly periods.
• Mixing balances or obligations: the result covers only the debt and savings amounts entered. It does not account for other debts, withdrawals, irregular deposits, or changes in payment.

For a precise debt payoff amount, use the balance and payment information supplied by the account issuer or servicer. For savings, use the account’s stated terms and consider whether the return is fixed or variable. The result is an estimate, and the lender’s disclosure gives the exact figures.

Frequently Asked Questions

Can I save money while paying off debt?
This calculator can estimate both at once, but it cannot determine an appropriate balance between them. Enter the monthly amount you expect to deposit and a separate debt payment to view the modeled outcomes.

What if my debt payment changes?
The payoff formula assumes the same payment every month. For changing payments, recalculate using a representative payment or model each period separately; this result will not reproduce an irregular schedule.

Does the savings balance include interest?
Yes. It includes monthly deposits plus estimated growth at the annual return you enter, compounded monthly. Actual earnings can differ, and the calculator does not subtract fees or taxes.

Why can’t the calculator estimate my payoff?
A payoff estimate is unavailable when the monthly payment does not exceed the first month’s interest. A zero or otherwise inadequate payment cannot reduce the debt under the calculation’s assumptions.

Is this a debt payoff quote?
No. It is an estimate using a fixed rate and monthly schedule. A creditor’s payoff figure may include accrued interest, fees, or timing details not represented here.

Related

• Capitalization of Unpaid Interest Calculator
• 263A(f) Interest Capitalization Calculator
• Capitalization of Construction Interest: How It Works

in bal | Debt balance | $ | 10000 | 0 | 100000000
in apr | Debt APR | % | 18 | 0.01 | 100
in pay | Monthly debt payment | $ | 500 | 0.01 | 100000000
in save | Monthly savings deposit | $ | 200 | 0 | 100000000
in savapr | Savings return (annual) | % | 3 | 0 | 100
in yrs | Savings period | years | 3 | 0.0833 | 50
out months | Months to pay off debt | months | ceil(round(-ln(1 - (apr / 1200) * bal / pay) / ln(1 + apr / 1200), 6)) | 0
out paid | Debt payoff status | months | months | 0
out fund | Savings balance at period end | $ | save * (((1 + savapr / 1200) ^ (yrs * 12) - 1) / (savapr / 1200)) | 2
out contrib | Total savings deposits | $ | save * yrs * 12 | 2