Portfolio Overlap Calculator
Paste two portfolios. See how much they actually overlap. Useful when you hold multiple strategies and want to know if you are diversifying or doubling up on the same tickers.
One ticker and weight per line (e.g. SPY 60). Weights can be %, decimals, or any unit; the tool normalizes to 100%.
Same format. Order does not matter. Duplicate tickers keep the first row.
Moderate overlap. Some shared exposure but each portfolio also brings distinct names.
| Ticker | Portfolio A | Portfolio B | Shared |
|---|---|---|---|
| SPY | 60.0% | 20.0% | 20.0% |
| GLD | 10.0% | 15.0% | 10.0% |
| VTI | — | 40.0% | — |
| AGG | 30.0% | — | — |
| TLT | — | 25.0% | — |
What does the overlap percentage mean?
The weight-overlap formula sums the smaller of the two weights for every ticker that appears in both portfolios: overlap = sum of min(weight_A, weight_B) per ticker. The result ranges from 0% (no shared tickers) to 100% (the portfolios are identical).
A useful rule of thumb: above ~70% the two portfolios are effectively interchangeable from a diversification standpoint. Between 30% and 70% they share significant exposure but each brings distinct names. Below 30% they are mostly independent.
This tool does not measure correlation, just weight overlap. Two portfolios with zero ticker overlap can still be highly correlated if both hold large-cap US equities through different ETFs (SPY vs VTI vs VOO). For full correlation analysis BestFolio Pro includes a correlation matrix view across all strategies.
BestFolio offers 98+ backtested portfolio strategies with monthly rebalancing signals. Build, blend, and backtest your own portfolio with full transaction-cost modeling.
Past performance is not indicative of future results. Overlap is a diversification metric, not a return forecast. Always do your own research before investing.
Portfolio Overlap Calculator: Frequently Asked Questions
- How is portfolio overlap calculated?
- The calculator normalizes each portfolio's weights to 100%, then sums the smaller of the two weights for every ticker the portfolios share. The result is the classic weight-overlap measure: 0% means no common holdings, 100% means identical portfolios. The per-ticker table shows how much each shared position contributes to the total.
- How much portfolio overlap is too much?
- There is no universal threshold; the percentage is the share of your money sitting in the same tickers in both portfolios. The higher it is, the less the second portfolio adds beyond the first. It is worth checking before blending two strategies, because a blend of heavily overlapping strategies diversifies less than the strategy count suggests.
- Does overlap measure correlation?
- No. Overlap counts shared holdings by weight, while correlation measures how returns move together. Two portfolios with zero ticker overlap can still be nearly perfectly correlated, for example one holding SPY and the other VOO, so treat overlap as a holdings check, not a substitute for return-based analysis.
- Does the overlap tool work for European and UCITS ETFs?
- Yes. The calculator is symbol-agnostic: paste any tickers with weights, including UCITS ETFs such as VWCE, IWDA, or CSPX, and the overlap is computed the same way. Because it matches tickers literally, translate both portfolios into the same listing first when you hold the US and the European version of the same fund.
- Do I need an account to use the overlap calculator?
- No. The tool is free and runs entirely in your browser: the portfolios you paste are parsed locally and never sent to a server. No signup is required.
- Can I compare my portfolio against a TAA strategy's allocation?
- Yes. Paste the strategy's current allocation as Portfolio B, one ticker and weight per line. BestFolio publishes current allocations for 6 strategies free without an account, so you can check how much a tactical strategy overlaps what you already hold.