Credit Card Interest Calculator

Estimate interest cost and payoff time on a card balance.

Key takeaways

  • Sections: How to use this calculator ยท How this calculator works ยท Methodology and limitations.
  • Criteria: the ranking method is published in full below - no paid placement changes it.
$
Outstanding principal on the card.
Annual percentage rate on purchases.
$
Amount you plan to pay each month.
Payoff time
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Total interest paid
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Educational tool only — not financial advice. Broker conditions, contract sizes, and pip values vary by instrument and account type; always confirm figures against your provider before trading.

How to use this calculator

Enter a value in each labelled field above. The defaults are sensible starting points, so you can see a complete result immediately and then adjust any single input. The tool recalculates on every keystroke, so the result cards always reflect your latest numbers — there is nothing to submit, no account to create, and no data is sent anywhere.

How this calculator works

The result you see is produced by a short formula that runs directly in your browser using the values you entered. There is no server round-trip: your inputs never leave this page, nothing is logged or stored, and the tool keeps working offline once the page has loaded. The formula itself is published in the page source, so anyone can audit exactly how each output is derived.

Under the hood, the math follows standard market conventions — percentage of account equity, distance in price or points, and notional contract value. Where a calculation depends on a convention that varies by broker (pip value, minimum tick size, margin percentage), we use the most common industry default and expose the relevant number as an input so you can override it with your own broker's value.

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Methodology and limitations

Every figure produced here is an estimate intended for planning and education. Real fills, spreads, swaps, financing charges, and currency conversions will move the final number, sometimes materially. Before placing an order, confirm the calculated size, margin, or P&L against your provider's own platform tools or trading agreement. Leverage magnifies losses as well as gains, and any calculation that assumes a fixed price path should be treated as a scenario rather than a forecast. This page does not constitute investment, tax, or financial advice.

Revolving credit compounds monthly, so small payments barely dent principal. This calculator iterates your payment against the monthly interest charge to show how many months a payoff takes and how much interest you will surrender.

Frequently Asked Questions

Why does minimum payment take so long?

Minimum payments are set near interest plus a sliver of principal, so balances can persist for decades at card APRs.