When your watchlist spans financials, miners, and consumer names, comparing raw price charts tells you little about which stock is actually outperforming. Relative strength (RS) lines solve this by measuring each name's performance against a common benchmark — typically the FTSE 350 index for UK equity watchlists.
What an RS line shows
An RS line plots the ratio of a stock's price to the benchmark index price over time. When the line rises, the stock is outperforming the index. When it falls, the stock is underperforming regardless of whether its absolute price is going up or down.
This distinction matters for watchlist ranking. A miner up 3% while the index is up 5% has a falling RS line — it is a laggard even though the price chart looks bullish.
Choosing your benchmark
For broad multi-sector watchlists, the FTSE 350 works well as a default. If your watchlist is concentrated in one sector — say, ten FTSE 250 mid-caps — consider using that sector's index instead. The goal is a benchmark that represents the opportunity cost of holding any name on your list.
In coaching sessions we often see traders use the FTSE 100 when their watchlist is mostly large-caps, or a custom equal-weight basket when comparing AIM names that sit outside major indices.
Reading slope, not level
The absolute level of an RS line matters less than its slope over the last four to six weeks. A name with a high RS level but flattening slope is losing momentum. A name with a lower RS level but steeply rising slope is gaining ground and may soon rank higher.
When building your weekly ranking table, record slope direction (rising, flat, falling) alongside the rank. Two names with similar RS levels but different slopes should not receive equal attention.
Common mistakes
- Using too short a lookback: RS lines on a five-day chart are noisy. Twelve weeks gives enough data to see genuine trends without lagging too far behind.
- Ignoring sector context: A falling RS line in a sector where every name is falling may still represent the best relative performer. Compare within sector groups first.
- Overreacting to single-day spikes: Wait for a full week's RS slope confirmation before changing rank.
Next step
Plot RS lines for every name on your current watchlist this weekend. Rank by slope within each sector group. If you want guided feedback on your rankings, our RS Watchlist Workshop includes individual review of your submitted list.