APR & FICO Explained

Two numbers determine what you pay on a credit card: your APR (how much interest you're charged on a balance) and your FICO (what APR you're offered in the first place). Understanding how both work — and more importantly, how to avoid the first and improve the second — is worth thousands of dollars over a lifetime of using credit. This guide walks through exactly how APR is calculated, how FICO is built, and the plays that move both in your favor.

1. How APR actually works

APR is expressed as an annual rate, but credit cards compound interest daily. The math: Daily rate = APR ÷ 365. At 24.37% APR, the daily rate is 0.0668%. Each day your balance is multiplied by 1.000668. Over 30 days, a $1,000 balance grows to about $1,020.25 — the $20.25 is your interest for that cycle.

Cards have three types of APR, usually listed separately in the cardholder agreement:

Purchase APR

Applies to new purchases that aren't paid off within the grace period. Typical range 18%–29%.

Balance transfer APR

Applies to balances moved from other cards. Often 0% during an intro period, then revert to the purchase APR.

Cash advance APR

Applies to cash withdrawals. Usually 27%–30%, and with no grace period — interest starts the day of the advance.

2. Grace period and why it matters

The Truth in Lending Act guarantees a grace period of at least 21 days on credit card purchases — the window between your statement close date and the due date. If you pay the full statement balance by the due date, you owe zero interest on those purchases, no matter what your APR is.

Critical detail: carrying any balance breaks the grace period on new purchases too. If you have a $1,000 balance you haven't paid off, and you make a new $200 purchase, interest on that $200 starts from the day of purchase — not after the next statement. This is called "losing the grace period" and is a big reason not to carry a balance.

3. The five FICO factors

FICO 8 (the most commonly used consumer score) weights five factors:

Factor	Weight	What it means
Payment history	35%	Whether you've paid on time. A 30-day late drops good scores 60–100 points.
Amounts owed / utilization	30%	How much of your available credit you're using. Under 10% is ideal; over 30% is penalized.
Length of credit history	15%	Average age of all accounts + age of oldest + age of newest. Closing old accounts hurts.
Credit mix	10%	Variety: credit cards, auto loans, mortgages, student loans. More variety helps slightly.
New credit / inquiries	10%	Hard inquiries and recently opened accounts. 5 pts per inquiry, typically recovers in 6 months.

4. FICO vs. VantageScore

Credit Karma, NerdWallet, and most free monitoring tools show you VantageScore — not FICO. Both range 300–850, but they weight factors slightly differently. VantageScore tends to be friendlier to thin files (it gives a score after 1–2 months; FICO needs 6 months) and slightly heavier on utilization. In practice, a person's VantageScore is usually 20–50 points higher than their FICO. Lenders use FICO. Don't be surprised when your '750 VantageScore' turns out to be a 715 FICO.

5. Improving your score in 90 days

Realistic lever-pulls, ranked by likely impact:

1. Pay down balances before the statement cuts. Utilization is 30% of your score and it's reported at statement close, not at the due date. Paying $500 on day 28 of a 30-day cycle drops reported utilization by $500 — worth 20–40 points if you were previously over 50%.
2. Ask for a credit limit increase. Most issuers let you request online. A higher limit reduces your utilization without requiring you to spend less.
3. Become an authorized user on an established card (parent, spouse). The account's history joins your file instantly.
4. Dispute errors on your credit report. The FCRA gives bureaus 30 days to verify or remove.
5. Pay down installment loans if you have the cash. Auto and student loans being 20%–30% paid down helps — though not as much as credit card utilization.

6. Disputing errors on your report

About 1 in 4 Americans has at least one error on their credit report, per an FTC study. Check all three reports free at annualcreditreport.com. File disputes directly with the bureau (Experian, Equifax, or TransUnion) — online is fastest. The FCRA requires them to investigate within 30 days. If the information can't be verified, it must be removed.

If a dispute is denied and you believe the denial is wrong, escalate to the CFPB at consumerfinance.gov/complaint. The bureaus usually take second-look action on CFPB-routed complaints.