Compare growth factors, not percentage-return ratios
A price-relative line divides one security’s price by another’s. To compare a chosen interval, this calculator divides the ending price ratio by the starting ratio: (S1 / B1) / (S0 / B0), equivalently (S1 / S0) / (B1 / B0). The result starts at one. See Fidelity’s relative-strength comparison definition.
Read three separate outputs
- Each price return is (end / start − 1) × 100%.
- Excess price return subtracts benchmark return from stock return, in percentage points.
- Normalized RS compares the two growth factors. Above one means the stock grew more or declined less; one means equal price returns; below one means it lagged. These statements require a positive benchmark ending price.
Examples that include falling markets
A stock rising from 100 to 125 and a benchmark rising from 4,000 to 4,400 produce returns of 25% and 10%, excess return of 15 percentage points, and normalized RS of 1.25 / 1.10 = 1.13636. This is not a claim that the stock returned 113.6%.
If both decline, −10% versus −20% gives 0.9 / 0.8 = 1.125. The stock outperformed while still losing money. If the benchmark is flat, the ratio remains defined. If its ending value is zero, the ratio is unavailable, but the two returns and their difference remain visible.
Choose comparable observations
Use identical dates and consistent price adjustment and return-currency conventions. Stock splits, distributions and foreign-exchange changes can distort mismatched series. Price return is not automatically total return. This tool does not annualize returns, rank a stock universe, calculate RSI, control for risk or predict future momentum.
Frequently asked questions
- What relative-strength formula does this calculator use?
- Normalized price-relative strength: (stock end / stock start) divided by (benchmark end / benchmark start). The starting relative value is one. It also reports each price return and their difference in percentage points.
- Why not divide the percentage returns?
- A percentage-return ratio is undefined when the benchmark is flat and can reverse its apparent meaning in falling markets. Comparing growth factors avoids those problems when the benchmark ending price remains positive.
- Can relative outperformance still lose money?
- Yes. A stock declining 10% while its benchmark declines 20% has normalized relative strength 0.90 / 0.80 = 1.125, but the stock investment still lost 10% before costs.
- Is this the same as RSI or a percentile RS rating?
- No. RSI is a single-series oscillator, while percentile RS ratings require a comparison universe. This calculator compares two manually entered price series over one matching interval.
- What data should I enter?
- Use the same start and end dates and a consistent adjustment and currency-return basis. Price returns omit dividends unless your input series already adjusts for them. No prices are fetched and no future returns are forecast.
Educational comparison, not investment advice.