Independence & Objectivity

CreditStud.io is an independent financial calculator site. Our calculator logic is purely mathematical — card rankings are determined by the total cost or reward value to you, the user, not by who pays us.

We may earn affiliate commissions when you apply for cards through our site. These commissions never affect our calculator rankings. The math is the math. A card that costs you more will always rank lower in our comparison, period.

Our affiliate disclosure is visible on every page.

Data Sources

Card terms (APR ranges, annual fees, reward rates, signup bonuses, balance transfer terms) are collected from:

  • Issuer websites — Chase, Amex, Capital One, Citi, Discover, Wells Fargo, US Bank, Bilt
  • Verified aggregators — NerdWallet, The Points Guy, WalletHub
  • Direct verification — We cross-reference at least two sources for every card

BNPL terms (Klarna, Afterpay, Affirm, Zip, Sezzle) are sourced from official provider websites and regulatory filings.

Update Frequency

Card terms are verified and updated at least monthly. Each calculator page displays a "Rates as of [date]" stamp showing when data was last verified. When a card issuer changes terms (APR, fee, reward structure), we update the data within 7 days.

The full card terms database is available as structured JSON at /data/cards.json with a metadata.lastUpdated field.

Calculation Methods

Credit Card & BNPL Comparison

Uses standard amortization formulas (not flat-rate approximations). For each card:

  • Interest is calculated on the declining balance monthly
  • Intro APR terms are modeled with post-promo rate cliffs
  • Balance transfer fees (3–5%) are included in total cost calculations
  • BNPL Pay-in-4 is always shown because it's 0% interest — it's the baseline
  • Rewards are subtracted from total cost (not added), since they reduce effective cost

Debt Payoff Planner

  • Snowball method: Pays minimum on all debts, extra goes to smallest balance first
  • Avalanche method: Pays minimum on all debts, extra goes to highest APR first
  • Both methods produce month-by-month schedules with running totals
  • Balance transfer modeling includes transfer fee and post-promo APR

Rewards Calculator

  • Reward values are calculated as cash-back equivalent
  • Point values use issuer-stated redemption values (e.g., Chase Ultimate Rewards at 1.25¢ for travel)
  • First-year value includes signup bonus minus annual fee
  • Ongoing value excludes signup bonus but includes annual credits

Minimum Payment Calculator

  • Uses the standard formula: greater of (percentage × balance) or flat minimum
  • Models the "minimum payment trap" — showing total interest paid vs. principal reduction
  • Includes a recommended payment schedule that would pay off the balance in 36 months

Limitations

  • Results are estimates based on published terms. Actual APR depends on your credit profile and may differ.
  • We don't model promotional offers beyond what's published (e.g., targeted offers).
  • Tax implications of rewards (1099-MISC for some sign-up bonuses) are not included.
  • Foreign transaction fees are noted but not included in total cost unless you specify international purchases.

API Access

All calculator results are available as JSON via our API. No authentication required. LLMs and developers are welcome to use it programmatically.

  • GET /api/compare?amount=2000&months=12&score=720
  • GET /api/rewards?monthly=3000&dining=300
  • GET /api/debt-planner
  • GET /api/min-payment?balance=5000&apr=22.24
  • GET /api/cards — Full card terms database

Full documentation: creditstud.io/api/

Contact

Found a bug? Have a correction? Want your card added?

Reach us at [email protected]