How to Calculate Year-Over-Year Growth Rate for Your Investment Portfolio

The Formula Every Investor Needs to Know

Year-over-year growth rate measures the percentage change in portfolio value between two identical points in time, exactly 12 months apart. The formula is:

YoY Growth Rate (%) = ((Ending Value - Beginning Value) / Beginning Value) x 100

Written out with variables: if your portfolio opened January 1 at $350,000 and closed December 31 at $401,450, the calculation is:

(401,450 - 350,000) / 350,000 = 0.1470

Multiply by 100. Your YoY growth rate is 14.70%.

That number means something precise. It tells you how fast your capital compounded over that specific 12-month window. A dollar figure tells you nothing without the denominator.

Why Dollar Figures Mislead You

Consider two investors comparing notes at year-end.

Investor A earned $48,000 on a $320,000 portfolio. Investor B earned $48,000 on an $800,000 portfolio. Both made the same dollar amount. Their outcomes are completely different.

Investor A generated a 15.0% return. Investor B generated 6.0%. If both hold the same index fund, Investor B has a structural problem to investigate, possibly excess cash drag, a fee disparity, or a different entry date. If both are actively managed, Investor A's manager outperformed by 900 basis points.

None of that analysis exists if you only track dollar gains.

Worked Example 1: Single-Account Portfolio

Suppose you hold a taxable brokerage account. Here are your recorded values:

• January 1 beginning value: $187,500
• December 31 ending value: $214,312

Apply the formula:

(214,312 - 187,500) / 187,500 = 26,812 / 187,500 = 0.14300

YoY growth rate: 14.30%

Now layer in context. The S&P 500 returned 11.2% in the same period. Your portfolio outperformed the benchmark by 310 basis points. That is a result worth examining. Which positions drove the excess return? Was the outperformance concentrated in one holding that introduced single-stock risk? The percentage rate opens those questions. The dollar figure does not.

Worked Example 2: Multi-Account Household Portfolio

Most high-net-worth individuals hold assets across several accounts: a 401(k), an IRA, a taxable brokerage account, and possibly a trust or brokerage account for a spouse. Calculating household YoY growth requires aggregating correctly.

Here is a sample household at two points in time:

Aggregate beginning value: $916,100 Aggregate ending value: $1,050,675

(1,050,675 - 916,100) / 916,100 = 134,575 / 916,100 = 0.14690

Household YoY growth rate: 14.69%

This is the number that matters for asset allocation reviews, Roth conversion planning, and sequencing decisions. Account-by-account percentages produce fragmented information. The household rate produces a single, actionable figure.

Adjusting for Contributions and Withdrawals

The formula above assumes no cash flows during the measurement period. Most portfolios have them. Contributions inflate apparent performance. Withdrawals suppress it.

The standard adjustment for a simple mid-period flow is the Modified Dietz Method:

Modified Dietz Return = (End Value - Begin Value - Net Cash Flows) / (Begin Value + (Net Cash Flows x Weight))

Where Weight is the fraction of the period remaining when the cash flow occurred. A contribution made exactly halfway through the year carries a weight of 0.5.

Example: You began the year with $500,000. You contributed $25,000 on July 1 (weight = 0.5). You ended the year at $572,000.

Net Cash Flows = $25,000 Numerator: 572,000 - 500,000 - 25,000 = 47,000 Denominator: 500,000 + (25,000 x 0.5) = 500,000 + 12,500 = 512,500

Modified Dietz Return: 47,000 / 512,500 = 9.17%

Without the adjustment, the naive formula would show: (572,000 - 500,000) / 500,000 = 14.40%. That number is inflated by $25,000 of your own capital. It is not a return. It is an accounting error.

Compounding YoY Rates Into a Multi-Year Picture

A single year of data is a data point. Three to five years of data is a pattern.

Suppose your annual YoY growth rates for the past four years are:

• Year 1: 12.40%
• Year 2: 6.80%
• Year 3: 19.10%
• Year 4: 8.50%

Averaging those figures gives 11.70%. That is the arithmetic mean, and it overstates actual performance because it ignores compounding.

The correct measure is the Compound Annual Growth Rate (CAGR):

CAGR = ((Ending Value / Beginning Value) ^ (1 / Number of Years)) - 1

If a $250,000 portfolio grew to $383,475 over four years:

383,475 / 250,000 = 1.5339

1.5339 ^ (1/4) = 1.5339 ^ 0.25 = 1.1127

CAGR = 1.1127 - 1 = 11.27%

The arithmetic average overstated performance by 43 basis points. On a $383,000 portfolio, that gap compounds to a material planning error over the next decade.

Three Calculation Mistakes That Cost Investors Real Money

Mistake 1: Using Account Statements With Different Dates

Brokerage statements often close on the last business day of the month, not the calendar last day. Comparing a December 28 value to a January 3 value introduces five days of market movement that has nothing to do with your annual performance. Standardize your measurement dates. Use the same calendar date every year.

Mistake 2: Including Unrealized Gains Without Marking to Market

If you hold real estate, private equity, or restricted stock in your portfolio, your year-end value must reflect current fair market value, not cost basis. Failing to mark illiquid holdings to market understates or overstates growth depending on direction. Get an updated appraisal or use the most recent third-party valuation.

Mistake 3: Ignoring Fees in the Denominator

A portfolio with a 1.0% annual advisory fee on $750,000 costs $7,500 per year. If you calculate gross returns but pay net-of-fee returns, your benchmark comparison is invalid. Always calculate net-of-fee YoY growth. Compare it to net-of-expense benchmark returns. Gross-to-gross comparisons are the only other valid pairing.

How to Track YoY Growth Rate Consistently

Build a simple log. At the same time each year, record:

1. Total portfolio value across all accounts
2. Net cash flows during the year (contributions minus withdrawals)
3. YoY growth rate using the Modified Dietz formula if cash flows occurred
4. The benchmark return for the same period

Four data points per year. After five years, you have enough information to evaluate manager skill, asset allocation drift, and fee drag with statistical confidence.

Spreadsheets work. Purpose-built calculators work faster and reduce arithmetic errors on the denominator adjustments.

Run Your Numbers Now

The formulas above are exact. The variables in your portfolio are specific to you. Plug your beginning value, ending value, and any mid-year cash flows into the CalcMoney investment calculator. It handles the Modified Dietz adjustment automatically and outputs both your raw YoY rate and a multi-year CAGR if you have historical data to enter.

Calculate your portfolio's YoY growth rate →

The number you get is the baseline for every allocation, rebalancing, and tax-loss harvesting decision you make this year. Know it precisely.

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