How to Calculate Credit Account Age Impact on Your Score

Credit Age Controls 15% of Your FICO Score

The FICO scoring model allocates exactly 15% of your score to the "length of credit history" category. On the standard 300-to-850 scale, 15% equals up to 82.5 raw points. For a borrower sitting at 720, a meaningful age drop can push them below the 680 threshold that triggers lender risk-tier changes.

FICO evaluates three sub-factors inside this category. First, the age of your oldest account. Second, the age of your newest account. Third, the average age of all open accounts. Average age carries the most weight in daily score calculations.

Experian, Equifax, and TransUnion all calculate average age in months, not years. This matters when you model the impact of closing or opening accounts.

The Average Account Age Formula

Average account age equals the sum of each open account's age in months, divided by the total number of open accounts.

Written as plain text:

Average Age (months) = Sum of all open account ages in months / Number of open accounts

Pull your current credit report from AnnualCreditReport.com. For each open account, calculate months open using: (Current Month and Year) minus (Open Date Month and Year). Sum every result. Divide by your account count.

FICO excludes closed accounts from this calculation after they age off your report, typically after 10 years for accounts in good standing and 7 years for derogatory accounts.

Worked Example 1: Closing an Old Card

A borrower holds five open credit accounts.

• Visa Signature opened January 2011: 174 months
• Mastercard World opened March 2016: 114 months
• Discover It opened August 2018: 85 months
• Chase Freedom Flex opened November 2020: 58 months
• Capital One Quicksilver opened May 2023: 16 months

Sum: 174 + 114 + 85 + 58 + 16 = 447 months. Divide by 5 accounts. Average age: 89.4 months, or 7 years and 5 months.

The borrower closes the 2011 Visa Signature to simplify their wallet.

New sum: 114 + 85 + 58 + 16 = 273 months. Divide by 4 accounts. New average age: 68.25 months, or 5 years and 8 months.

The drop: 21.15 months, or 1 year and 9 months of average credit age, erased instantly. FICO research correlates a drop of this magnitude with a score decline of 15 to 40 points, depending on the full profile.

At 700 before the closure, this borrower may land between 660 and 685. A 30-year fixed mortgage on a $400,000 purchase at 700 might price at 6.85%. At 665, that same lender may quote 7.30%. On a $400,000 loan, that 0.45% difference costs $42,840 in additional interest over 30 years.

Worked Example 2: Opening a New Account

A borrower holds three open accounts.

• American Express Gold opened February 2015: 136 months
• Citi Double Cash opened July 2019: 74 months
• Bank of America Cash Rewards opened January 2022: 32 months

Sum: 136 + 74 + 32 = 242 months. Divide by 3. Average age: 80.7 months, or 6 years and 8 months.

The borrower opens a new Chase Sapphire Preferred in September 2026: 0 months.

New sum: 136 + 74 + 32 + 0 = 242 months. Divide by 4. New average age: 60.5 months, or 5 years and 1 month.

The drop: 20.2 months, without closing a single account. New accounts damage credit age even though they add tradelines. The hard inquiry from the application adds a separate 5-to-10-point penalty on top of the age impact.

This borrower should open new accounts only when the credit limit boost, the sign-on bonus, or the rate reduction justifies the multi-year score recovery period.

How Long Closed Accounts Extend Your Score Buffer

Closed accounts in good standing remain on your credit report for 10 years from the closure date. During that window, FICO still counts them in your average age calculation. This creates a common error: borrowers assume a closed account immediately disappears. It does not.

If the borrower in Example 1 closes the 2011 Visa Signature in September 2026, that account stays on the report until September 2036. For the next decade, it continues contributing 174-plus months to the average age sum.

The real damage hits in 2036, when the account ages off entirely. Plan accordingly. If a long-tenured closed card will age off within five years, the score hit is approaching regardless. Opening new accounts now to build future age depth is the rational response.

The Authorized User Account Calculation

Becoming an authorized user on a spouse's or parent's account adds that account's full history to your credit report. FICO counts authorized user accounts in average age calculations.

A borrower with three accounts averaging 36 months adds an authorized user account that is 144 months old. New average: (36 x 3 + 144) / 4 = (108 + 144) / 4 = 252 / 4 = 63 months. Average age jumps from 36 months to 63 months without opening a new account or taking a hard inquiry.

The primary account holder's payment history on that account also appears on the authorized user's report. Select primary holders with spotless payment records.

Calculate the Dollar Cost Before Every Credit Decision

Every credit decision with an age impact deserves a dollar-cost projection before execution. Calculate the average age formula with and without the proposed action. Then price the score difference against a mortgage, auto loan, or personal loan using current lender rate tiers.

A 25-point score drop that saves $95 in annual fees costs you nothing if you plan no major borrowing in the next 24 months. The same 25-point drop costs $28,000 in mortgage interest if you plan to buy a home next spring.

The CalcMoney Debt Snowball Calculator lets you model payoff timelines across multiple accounts. Input your current balances and rates to identify which accounts to eliminate first, without accidentally closing the ones that anchor your credit age.

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Results are estimates for informational purposes only. Consult a licensed financial professional before making financial decisions.