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Performance Measurement

How to Benchmark Your Portfolio vs. the S&P 500

By The TradeReveal Team•January 20, 2026

You think you beat the market this year. You probably did not benchmark your portfolio against the S&P 500 in a way that would survive scrutiny.

Most traders compare a rough account return against whatever S&P 500 number they saw in a headline. That comparison is almost always unfair to one side. You might be counting price-only index gains against your dividend-inclusive account, or comparing a full year of the index against six months of your own capital, or letting a mid-year deposit inflate your dollar growth and calling it skill.

This guide shows you how to do the comparison honestly: which S&P 500 number to use, which return calculation neutralizes your deposits and withdrawals, how to align time periods, and how to read the result without fooling yourself.

TL;DR

  • Compare against the S&P 500 Total Return index, not the price index you see quoted on TV, so dividends are on both sides.
  • Use time-weighted return (TWR) for your portfolio, because it strips out the effect of when you added or removed cash.
  • Align the exact start and end dates of both series, and subtract your own fees and commissions before comparing.
  • A one-year "win" is noise. Judge the comparison over multiple years and against your own risk.
  • About 65% of professional large-cap funds trailed the index in 2024, and roughly 90% trailed it over 15 years, so beating it is rarer than it feels (per S&P Dow Jones Indices SPIVA data).

Why a naive comparison lies to you

Say your account started the year at $50,000 and ended at $60,000. That is a 20% gain, and the S&P 500 "was up about 15%," so you beat the market by five points. Clean story. Usually wrong. Three things can quietly break it:

  1. Cash flows. If you deposited $8,000 in March, most of that $10,000 increase is your own money, not investment return. Your true return might be closer to 4%.
  2. The wrong index. The S&P 500 figure quoted in the media is the price return index, which ignores dividends. Your account collected and often reinvested dividends. You are comparing a number that includes income against one that does not.
  3. Mismatched windows. If you funded the account in April, your capital was only exposed for nine months while the index number covers twelve.

Fix all three and the comparison becomes fair. Skip any one and the answer is decorative.

Use the total return index, not the price index

The number you hear on financial news ("the S&P 500 closed up 0.8%") is the price return index. It tracks the change in the market value of the 500 constituents and ignores the dividends those companies pay.

The S&P 500 Total Return index assumes each dividend is reinvested on its ex-dividend date, so it captures both price appreciation and income. S&P Dow Jones Indices, which publishes the index, is explicit that the headline S&P 500 is a price return index while the total return version reflects reinvested dividends. See the S&P Dow Jones Indices FAQ on the S&P 500 Dividend Points Index for the definitions.

The gap is not trivial. In 2025, the S&P 500 price index returned about 15.96%, while the total return version returned roughly 17.44% once dividends were reinvested, according to return data compiled by DQYDJ. Over decades, reinvested dividends compound into a large share of total equity returns. Benchmarking your dividend-collecting account against a price-only index hands the index a handicap and flatters your own numbers.

Which version matches you?

  • If you reinvest dividends, compare against the S&P 500 Total Return index.
  • If you take dividends as cash and spend them, the price return index plus your realized dividend income is the closer match. Most active traders reinvest or keep the cash in the account, so total return is usually right.

Use time-weighted return to neutralize your deposits

Once the index side is fair, fix your side. The core problem is cash flows: money you add or withdraw during the period changes your ending balance without reflecting how your picks actually performed. There are two standard ways to compute a return, and they answer different questions.

Time-weighted return (TWR) removes the effect of cash-flow timing. It breaks the period into sub-periods at each deposit or withdrawal, computes the return of each, and links them together. Because it ignores when money entered or left, TWR isolates the performance of the strategy itself. This is the return the investment industry uses to compare managers against benchmarks, and it is the method prescribed by the CFA Institute's Global Investment Performance Standards (GIPS), as summarized in AnalystPrep's GIPS study notes.

Money-weighted return (MWR), mathematically the internal rate of return, includes the size and timing of your cash flows. It answers "what did my capital actually earn," which is useful for judging your funding decisions, but it makes for an unfair benchmark comparison. If you happened to deposit right before a rally, MWR credits your return with luck that the index never had. PWL Capital lays out the distinction clearly in Calculating and Understanding Your Portfolio Returns: TWR is the metric for comparing against an index, MWR for measuring your personal experience.

For benchmarking against the S&P 500, use TWR. Track MWR alongside it if you want to see whether your contribution timing helped or hurt, but never put MWR head to head with the index.

If your broker or tracker already reports TWR, use it. If you are computing by hand and lack a portfolio valuation at each cash-flow date, the Modified Dietz method is the accepted approximation: it weights each cash flow by the fraction of the period it was invested and needs only the beginning value, ending value, and the dates of the flows. Corporate Finance Institute gives the formula and a worked example in its note on the Modified Dietz method. GIPS accepts Modified Dietz as a stand-in for true TWR when intra-period valuations are not available.

Align the time periods exactly

A benchmark comparison is only valid if both series cover the identical window, down to the day.

Grab the S&P 500 Total Return index level on your start date and on your end date. Your index return is:

Index return = (ending level - starting level) / starting level

Compute your TWR over the same two dates. If you funded the account partway through the year, do not compare your partial-year return against a full-year index number. Either shorten the index window to match your funding date, or compare full months where both sides have data.

A few alignment traps:

  • Partial first year. New account funded in April? Benchmark April-to-December on both sides, not January-to-December.
  • Trading days, not calendar days. The index only prints on trading days. Use the nearest trading day for your endpoints on both series.
  • Currency. If you report your portfolio in a currency other than US dollars, the index is dollar-denominated. Convert one side so both are in the same currency, or the exchange-rate move will masquerade as skill or shortfall.

Subtract your own costs before you compare

The S&P 500 Total Return index is frictionless. It pays no commissions, no spreads, and no data fees. You do. To compare like with like, your benchmark number should be net of your trading costs.

If you tracked gross returns, subtract commissions, financing costs, and any platform fees over the period, then compare that net figure against the index. This is exactly why beating the index is hard: you are not just competing with the market's return, you are competing with it after paying to participate. An account that matches the index gross underperforms it net.

Read the result honestly

Once the comparison is fair, resist the urge to over-read a single year.

One year is noise. Judge the gap over several years. A strategy can beat the index for twelve months on luck and give it all back in the next drawdown. That is the base rate, not pessimism. According to the S&P Dow Jones Indices SPIVA U.S. Year-End 2024 Scorecard, roughly 65% of actively managed large-cap U.S. equity funds underperformed the S&P 500 in 2024, and the shortfall widens over time: about 90% of large-cap funds trailed the index over the 15 years ending December 2024. The long-horizon persistence of that underperformance is covered by Institutional Investor, reporting on the same S&P data. Professionals with research teams mostly lose this race. A retail account beating the index over one year has proven very little.

Adjust for risk. Beating the index by concentrating in three volatile names is not the same accomplishment as matching it with a diversified book. If your outperformance came with far larger swings, you took more risk to get there. Look at your worst peak-to-trough decline over the period next to the index's, so the comparison accounts for how much pain each return demanded. Our guide on how to calculate portfolio drawdown walks through measuring that directly.

Separate realized from paper gains. If your outperformance sits in open positions, it is not banked yet. A benchmark that looks good on unrealized winners can reverse before you close them, which is why it helps to keep realized and unrealized P&L distinct when you judge the result.

Confirm the index even fits. If you trade small caps, crypto, or futures, the S&P 500 is the wrong yardstick, and any comparison against it is meaningless. Match the benchmark to what you actually trade. We cover the selection logic in how to choose a benchmark index.

Where this fits in your tracking

Doing this by hand once is instructive. Doing it every month across deposits, dividends, and multiple currencies is tedious and error-prone. If you are still setting up the basics, start with our walkthrough on how to track your portfolio performance and layer the benchmark comparison on top once your data is clean.

A dedicated journal like TradeReveal can compute a time-weighted return from your logged positions and cash in your chosen reporting currency, which removes much of the alignment work above. Whatever you use, the discipline is what matters: fair index, fair return method, matched dates, net of costs.

Frequently Asked Questions

Should I use the S&P 500 price return or total return index?

Use the total return index if you reinvest dividends, which most active accounts effectively do. It reflects reinvested dividends on both sides, so you are not comparing your income-inclusive account against a price-only index. Use the price return index only if you take dividends out as cash and spend them, and even then add your realized dividend income back to your own side.

Why does time-weighted return matter for benchmarking?

Because it removes the effect of when you added or withdrew money. A big deposit before a rally can make your money-weighted return look strong even if your picks were mediocre. Time-weighted return isolates the performance of the strategy, which is the only thing the index can be fairly compared against. Money-weighted return still has value for judging your funding timing, just not for the benchmark.

How do I handle deposits and withdrawals during the year?

Split the period at each cash flow, compute the return of each sub-period, and link them (that is TWR). If you cannot value the portfolio on each cash-flow date, use the Modified Dietz method, which weights each flow by the fraction of the period it was invested and needs only start value, end value, and the flow dates.

Is beating the S&P 500 in one year a big deal?

Not on its own. About 65% of professional large-cap funds trailed the index in 2024, and roughly 90% trailed it over 15 years, per S&P Dow Jones Indices SPIVA data. A single strong year is well within the range of luck. Consistent outperformance over several years, at comparable risk, is the meaningful signal.

What if I trade something other than large-cap U.S. stocks?

Then the S&P 500 is the wrong benchmark. Match the index to your universe: a small-cap index for small caps, a total-market or sector index where appropriate, and a different reference entirely for crypto or futures. Benchmarking a small-cap or crypto book against the S&P 500 produces a comparison that means nothing.

Final Thoughts

"Did I beat the market" is a fair question with an unfair default answer, because the easy version of the comparison stacks the deck. Put both sides on equal footing first: the total return index against your time-weighted return, over the same dates, net of your costs. Then read the result over years rather than months, and against your own risk. Do that and the answer means something, whether it flatters you or not. Most of the value is in the honesty of the measurement, not the verdict.

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Happy Trading,

The TradeReveal Team

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