Separate interest from progress on the balance
For a $2,000 balance at 24% APR, the calculator’s monthly model starts with $40 interest. A $75 payment then reduces principal by $35. After that first modeled payment, $1,965 remains. The next month’s interest is $39.30, so another $75 payment reduces principal by $35.70.
| Modeled month | Interest | Principal reduction |
|---|---|---|
| 1 / $2,000 starting balance | $40.00 | $35.00 |
| 2 / $1,965 starting balance | $39.30 | $35.70 |
The payment is unchanged while the interest portion becomes smaller as the modeled balance declines. This explains the calculator’s behavior; your issuer’s statement may use a different daily calculation.
Use a statement checklist before trusting a comparison
- Identify the balance you intend to model, rather than substituting the original purchase amount.
- Check whether the statement separates purchases, transfers or cash advances at different APRs. One entered APR cannot represent every category accurately.
- Enter the monthly amount you intend to keep paying. A changing minimum due is not the same as this fixed-payment plan.
- To choose a finish timeframe instead, select “My monthly payment” and enter a whole number of months. The tool finds a fixed payment rounded up to a cent, then estimates interest using that payment. Keep new purchases and fees outside either mode; ongoing charges make these payoff paths inappropriate.
- Compare the modeled totals with the issuer’s disclosures and request an account-specific explanation when they differ.
Why the statement and this model can disagree
The CFPB explains that many issuers use average daily balances and daily interest. Payment timing and different APR categories can therefore matter. This tool applies one monthly rate and does not reproduce those daily balances.
A grace period or expiring promotion also changes what an entered APR represents. A 0% scenario here assumes that rate continues through payoff; it is not a promise about a card’s future terms. The final modeled payment may be smaller, so multiplying months by the regular payment can overstate total repayment.
For a base-versus-extra payment comparison on one balance, use Debt Freedom. Its two paths share the same monthly model, rather than adding lender-specific accuracy.
Example arithmetic checked against our calculator. Educational estimates; changing prices and personal circumstances can change results.