The Universal Calculation Engine
Insights
The Universal Calculation Engine

Payoff time rule of thumb

Part of: Credit Card Debt Trap

To compare two credit card balances offers, line up the time period, the balance the rate uses, and the cash you pay today—then look at the numbers.

Compare fairly

You cannot pick the better credit card balances deal until you are comparing the same months or years, the same balance or subtotal, and the same points and fees. Credit Card Debt Trap helps when two documents use similar words for different things.

What hides in the footnotes

Headline rates diverge in the fine print: how fees are financed, how interest days are counted, which balance accrues interest. It helps to read one explanation alongside another so you notice what you assumed.

One sentence per offer

Write one plain sentence for each offer: what rate, on what balance, over how long, with how much cash today. If you cannot write both, you are not ready to compare the headline percentages alone.

Checklist

Line this up firstWhy the “winner” changes
Same time unit?A monthly rate and an annual rate are not the same thing.
Same balance?A lower % on a larger balance can cost more than a higher % on a smaller one.
Same cash today?Points and fees change APR and total cost—use dollars, not slogans.
Same period, same balance, same cash up front
Then compare total cost

Same years, both offers

Core lesson

Go deeper: Credit Card Debt Trap. Use the calculators below with your own loan or bill numbers, not only the examples on this page.

Use the calculator

FAQ

Where is the main lesson?

Credit Card Debt Trap pulls the topic together in one place, with links to related lessons.

Which calculator should I open first?

Use the first tool in the list for most questions. If you are reconciling payment rows on a schedule, pick amortization when it appears in the list.