#18: Credit Scores

This is part of a series in which we re-evaluate Money Magazine’s “25 Rules To Grow Rich By”. One “rule” will be re-evaluated each weekday until the series concludes; you can keep tabs on the action at the 25 Rules index.

Rule #18: The best way to improve your credit score is to pay bills on time and to borrow no more than 30% of your available credit.

In the United States, the most common type of credit score is the FICO score (or Fair Isaac Corporation score). From the Wikipedia credit score entry:

Although the exact formulae for calculating credit scores are closely guarded secrets, Fair Isaac has disclosed the following components and the approximate weighted contribution of each:

* 35% punctuality of payment in the past (only includes payments later than 30 days past due)
* 30% the amount of debt, expressed as the ratio of current revolving debt (credit card balances, etc.) to total available revolving credit (credit limits)
* 15% length of credit history
* 10% types of credit used (installment, revolving, consumer finance)
* 10% recent search for credit and/or amount of credit obtained recently

Money’s rule seems to directly address the first two: pay your bills on time to reduce late payments, and reduce your credit card debt to improve your debt ratio. But where does that 30% number come from?

The fact of the matter is that there is no specific number that qualifies as a “good” ratio, just that lower is always better. Different reporting agencies use different formulas to calculate a “good” and a “bad” debt ratio and don’t disclose the actual contents of the formula, leaving you to guess what is best.

In short, you shouldn’t necessarily feel good if your credit ratio is below 30%. You should feel good if your credit ratio is lower now than it was six months ago, as every time you decrease your ratio, you help your credit score.

Another tip is that by canceling credit cards, you’re actually hurting yourself in two ways. First, you’re reducing the total available revolving credit that you have without reducing the amount of current debt you have, thus raising your credit ratio. Second, by eliminating lines of credit, you’re shortening your credit history. Simply put, if you’ve already got a credit card and paid it off, don’t cancel it; put it away somewhere safe.

Let’s rewrite that rule.

Rewritten Rule #18: The best ways to improve your credit score is to pay bills on time, to reduce the balance on your credit cards, and to not cancel old cards when you’ve paid off their balance.

Jump back to rule #17.

Trent Hamm

Founder & Columnist

Trent Hamm founded The Simple Dollar in 2006 and still writes a daily column on personal finance. He’s the author of three books published by Simon & Schuster and Financial Times Press, has contributed to Business Insider, US News & World Report, Yahoo Finance, and Lifehacker, and his financial advice has been featured in The New York Times, TIME, Forbes, The Guardian, and elsewhere.