Equal weight index builder: build an equal weighted index and test it against the S&P 500.
Pick the holdings, set every one to the same weight, and see what that rule would actually have done. Then flip the same list to market cap weighting and compare the two side by side over real market history.
Educational only · Never places a trade
In short
An equal weight index gives every holding an identical share of the portfolio, 1 divided by the number of holdings, instead of letting the largest companies dominate. The effect is dramatic: in July 2026 the ten biggest positions were 36.33% of a cap weighted S&P 500 fund and 2.50% of the equal weighted version of those same 500 companies. Equal weighting buys breadth and a small and value tilt, and pays for it with higher fees, higher turnover and stretches of underperformance when mega caps lead. You can buy that one fixed rule on one fixed list as an ETF, or build the rule on a list you choose yourself and backtest it first.
Last updated July 2026
Equal weight index vs market cap
Equal weighted index versus market cap weighted, on the numbers
Same 500 companies, two weighting rules. Fund figures are from the Invesco S&P 500 Equal Weight ETF and the Vanguard S&P 500 ETF profiles as of July 2026. Funds change, so confirm before you act on them.
| What you are comparing | Equal weight | Market cap weight |
|---|---|---|
| Weighting rule | Every holding gets the same weight, 1 divided by the number of holdings | Weight follows market value, the biggest company gets the biggest slice |
| Top 10 holdings share | 2.50% of the fund (RSP, July 2026) | 36.33% of the fund (VOO, July 2026) |
| Expense ratio | 0.20% (RSP) | 0.03% (VOO) |
| Rebalancing | Quarterly reset back to equal, third Friday of March, June, September and December | Drifts continuously, no reset needed |
| Built-in bias | Trims what ran up, adds to what lagged, so it tilts smaller and more value | Rides the winners, so it tilts larger and more growth |
| Turnover and tax drag | Higher, the quarterly reset trades every position | Very low, weights maintain themselves |
The concentration line is the one worth sitting with. A cap weighted S&P 500 fund held 520 companies in July 2026, but a third of your money was in ten of them. The equal weighted version of the same universe put 2.50% in its ten largest positions. Whether that is good or bad depends entirely on whether you think the mega caps deserve their weight. It is not a question a backtest answers for you, but a backtest will at least tell you what each answer would have cost.
The cost side is real too. The equal weighted ETF charged 0.20% against 0.03% for the cap weighted one, roughly seven times more, and the quarterly reset generates turnover that a cap weighted fund simply does not have. In a taxable account that turnover shows up as realized gains. The deeper version of this trade off is in market cap vs equal weight.
The mechanics
How an equal weighted index is calculated and reset
The formula is the least interesting part. Each of your N holdings gets a weight of 1/N, so 25 names means 4% each and 50 names means 2% each. The index return for a period is the sum of each holding's return multiplied by its weight. With equal weights that collapses to a simple average of the individual returns, which is why an equal weighted index is sometimes described as the average stock rather than the market.
The interesting part is what happens next. The moment prices move, the weights stop being equal. A holding that doubles while the rest stay flat becomes a much bigger slice of the index, and left alone for long enough an equal weighted index drifts back toward cap weighting. That is why every real equal weight index has a reset schedule written into its methodology. S&P Dow Jones Indices resets the S&P 500 Equal Weight Index back to roughly 0.2% per constituent effective after the close on the third Friday of March, June, September and December. Four days a year the index is exactly equal weighted. The rest of the time it is drifting.
A worked example
Take four stocks at 25% each on a $100,000 index. Over a quarter one rises 40%, one rises 10%, one is flat and one falls 20%. The index is up 7.5%, the simple average of the four returns. But the winner is now 30.2% of the index and the loser is 18.6%. At the reset you sell down the winner and buy the loser back to 25% each. Nobody has to have an opinion for that to happen; the rule does it.
Why the reset is the strategy
That mechanical trimming is where the equal weight tilt actually comes from, not from the 1/N formula. It is a systematic sell high and buy low applied without judgment four times a year. It works when moves mean revert and it hurts when a winner keeps winning for years, which is exactly what happened during the mega cap run. How often you reset matters more than most people expect, which is covered in index rebalancing explained.
One practical note that catches people out: an equal weighted index is not the same as an equal risk or equal volatility index. Giving a quiet utility and a volatile small cap the same dollar weight means the volatile name contributes far more to the swings. If what you want is balanced risk rather than balanced dollars, equal weighting is not the scheme you are looking for. The full set of options is in weighting schemes.
Read this before you commit
What equal weighting actually buys you, and what it costs
What it genuinely gives you
- Concentration control. No single company can quietly become a tenth of your portfolio because it had a good three years.
- A structural small and value tilt, because every company gets the same weight whether it is the largest in the country or the 480th.
- Forced discipline. The reset trims what ran up and adds to what lagged on a fixed calendar, with no decision required from you.
- Honest breadth. If you picked 40 names because you believed in 40 names, equal weighting is the only scheme that actually expresses that.
What it costs you
- Fees. The equal weighted S&P 500 ETF charged 0.20% versus 0.03% for the cap weighted one in July 2026.
- Turnover and tax. Every reset sells appreciated positions, and in a taxable US brokerage account those are realized gains you owe on.
- Tracking pain. There are multi year stretches where equal weight lags badly and you have to keep holding it anyway.
- Liquidity drift. Equal weighting pushes real money into the smallest names in the list, which trade thinner than the giants.
The claim you should be most suspicious of is that equal weighting simply beats cap weighting. Any chart making that case starts and ends on dates that were chosen. Run it from 2015 to 2024 and cap weighting wins comfortably. Run it across other windows and the ranking flips. Test your own start and end dates and look at the worst drawdown alongside the return, because the drawdown is the number that decides whether you would have still been holding at the end.
Indexes is educational and informational software, not investment advice. It never places trades, connects to a brokerage or holds assets. Backtests are hypothetical and past results never predict future returns.
How it works
Build an equal weighted index in four steps
Choose the holdings
Add the stocks or crypto tokens the index should hold. This is the part an off the shelf equal weight fund never lets you change.
Set equal weighting
Every holding gets 1/N. Switch to market cap or your own weights at any point to see how much the scheme alone is driving the result.
Backtest both versions
Run the same list under both rules over the same window and read the return, the volatility and the worst drawdown for each.
Set the reset cadence
Quarterly matches the S&P methodology. Test annual and drift band resets too, since cadence changes turnover more than it changes return.
Who equal weights
What people build equal weighted
A conviction basket
You researched 20 companies and believe in all 20. Cap weighting would put most of the money in the three you happen to already know best. Equal weighting expresses the actual thesis.
A de-concentrated core
People who are uncomfortable with how much of the S&P 500 sits in a handful of mega caps but do not want to leave large cap US equities entirely.
A sector or theme index
Thematic baskets are where cap weighting does the most damage, because one incumbent usually dwarfs the pure plays you actually wanted exposure to. See thematic investing.
An equal weighted crypto basket
Cap weighted crypto baskets are mostly Bitcoin. Equal weighting the same coins is a genuinely different asset, and worth backtesting before you hold it. See crypto index.
A weighting scheme bake off
Holding the list constant and changing only the weighting rule is the cleanest experiment in index design, because it isolates one variable instead of two.
A direct indexing design
Working out what weights you would want a managed account to hold before you fund one. See direct indexing.
Questions
Equal weight indexes, answered
What is an equal weight index?
An equal weight index gives every holding the same share of the portfolio regardless of company size. If the index holds 50 stocks, each one is 2% of it. That is different from a market cap weighted index, where a company worth ten times more gets ten times the weight. Equal weighting is a deliberate choice to spread exposure evenly across the whole list.
How do you calculate an equal weighted index?
Assign each of the N holdings a weight of 1/N, so 25 holdings means 4% each. Multiply each holding return by its weight and add them together to get the period return. Because prices move, real weights drift away from 1/N immediately, which is why an equal weighted index has to be reset on a schedule. Without the reset it quietly turns back into a cap weighted index.
Is an equal weight index better than market cap weighting?
Neither is better in every period. Equal weighting historically added return in stretches when smaller companies led and gave it back during mega cap runs, and it costs more in fees and turnover. What it reliably does is cut concentration. That is the honest way to frame it: you are buying breadth and paying for it with cost and tracking difference, not buying free outperformance.
What are the pros and cons of an equal weighted index?
The pros are lower single stock concentration, a natural small and value tilt, and a mechanical discipline that trims winners. The cons are higher expense ratios, higher turnover that creates taxable gains in a brokerage account, more exposure to smaller and less liquid names, and long periods of lagging when a handful of large companies drive the market.
How often is the S&P 500 Equal Weight Index rebalanced?
Quarterly. S&P Dow Jones Indices resets every constituent back to an equal share, roughly 0.2% each, effective after the close on the third Friday of March, June, September and December. Between those dates the weights drift with prices, so the index is only exactly equal weighted on four days a year.
Can you buy an equal weight index fund?
Yes. The best known US vehicle is the Invesco S&P 500 Equal Weight ETF, which carried a 0.20% expense ratio and 509 holdings in July 2026. Buying it gives you one fixed rule applied to one fixed list. Building your own equal weighted index instead lets you choose the list, which is the part an off the shelf fund never lets you change.
Why does equal weighting reduce concentration risk?
Because size stops mattering. In July 2026 the ten largest holdings were 36.33% of a cap weighted S&P 500 fund and 2.50% of the equal weighted version of the same 500 companies. Same companies, same universe, radically different single stock exposure. If your worry is that a few mega caps now drive most of the index, that number is the whole argument.
Does an equal weighted index work for crypto?
It changes the picture more than it does in equities. A market cap weighted crypto basket is dominated by Bitcoin, often 70% or more, so it mostly tracks Bitcoin. Equal weighting the same coins gives the smaller assets real influence, which raises volatility and dispersion sharply. Backtest both versions before you decide which one you actually want.
Weight it your way, then check the math
Build an equal weighted index from any stocks or crypto, flip it to market cap weighting, and see what the rule alone was worth over real history. No account, no minimum, no trades. Educational and informational only.