What this relative strength calculator does
Relative strength, in this context, means how well one asset performs compared to another reference asset (usually an index like the S&P 500). Instead of asking, “Did my stock go up?” we ask, “Did my stock do better than the benchmark?”
This page calculates four useful outputs: your asset return, benchmark return, outperformance in percentage points, and a relative strength ratio. Together these help you quickly identify leadership and laggards in a portfolio, watchlist, or sector rotation strategy.
Formula used
Step 1: Calculate each return
Asset Return = (Asset End Price − Asset Start Price) / Asset Start Price
Benchmark Return = (Benchmark End Price − Benchmark Start Price) / Benchmark Start Price
Step 2: Compare performance
Outperformance (percentage points) = Asset Return − Benchmark Return
Relative Strength Ratio = (1 + Asset Return) / (1 + Benchmark Return)
- Ratio > 1.00: asset outperformed benchmark
- Ratio = 1.00: asset matched benchmark
- Ratio < 1.00: asset underperformed benchmark
Quick interpretation guide
- Positive outperformance: your asset is stronger than the benchmark over that period.
- Negative outperformance: your asset lagged the benchmark.
- Small edge: may be noise over short windows.
- Persistent edge: often more meaningful when repeated across multiple periods.
Worked example
Suppose your stock moves from 100 to 125 (+25%), while the benchmark moves from 100 to 110 (+10%). Outperformance is +15 percentage points. The ratio is 1.25 / 1.10 = 1.1364, meaning your stock delivered roughly 13.64% stronger growth than the benchmark baseline.
Relative strength vs RSI (important)
Many traders confuse relative strength with RSI (Relative Strength Index). They are not the same:
- Relative strength (this tool): compares one asset to another asset/index.
- RSI: a momentum oscillator based on an asset’s own recent gains/losses.
If your goal is “is this stock beating the market?”, this calculator is the right fit. If your goal is “is this stock overbought/oversold?”, use an RSI calculator.
Best practices when using relative strength
1) Use matching time windows
Always compare the same dates. A mismatch creates misleading conclusions.
2) Check multiple periods
One week can be random. Look at 1, 3, 6, and 12-month windows for a more reliable view.
3) Pair with risk measures
A high-return asset may also be very volatile. Consider volatility, drawdown, and position sizing alongside relative strength.
4) Avoid single-metric decisions
Relative strength is powerful, but it works best with fundamentals, trend structure, and a clear risk plan.
Final thoughts
A relative strength calculator gives you a clean, data-driven way to judge whether an investment is truly pulling its weight versus a benchmark. Use it consistently, compare apples to apples, and focus on repeatable process over one-off results.