Relative strength and RSI measure different things
Relative strength against a benchmark compares two securities. RSI, the Relative Strength Index, calculates an oscillator from changes in one security’s price. Their similar names are a reliable source of confused chart notes.
Compare two paths
Suppose a hypothetical stock rises from $100 to $110 while an index rises from 1,000 to 1,050. Over the same dates, the stock gains 10% and the index 5%. A ratio of the stock price to the index moves from 0.1000 to about 0.1048.
That rising ratio describes relative outperformance. If both fall, the stock can still outperform by falling less. Record absolute changes alongside the comparison so relative strength does not conceal a loss.
RSI uses another calculation
RSI ranges from zero to 100 and reflects the relationship between upward and downward price changes over a chosen period. Conventional levels such as 70 and 30 are reference settings, rather than guaranteed reversal points. Strong trends can keep readings elevated or depressed.
Label the two tools clearly in your workspace. Include the benchmark for relative strength and the period for RSI. A note saying only “strong” leaves the measurement undefined.
Try the comparison with a broad index and a sector index. A company may outperform the broad market while lagging its peers. Both observations can inform research, though neither supplies a complete investment decision.
Use matching dates, currency and adjustment conventions. Comparing a dividend-adjusted stock series with an unadjusted benchmark adds a data difference to the performance comparison.