How to Read Stock Heatmaps
A practical guide to using stock market heatmaps for trading decisions — size modes, color interpretation, and sector analysis.
What Is a Stock Heatmap?
A stock heatmap is a visual representation of market data where each stock is displayed as a rectangle. The color indicates performance (green for gains, red for losses), and the size can represent different metrics like market capitalization or percentage change.
Heatmaps let you absorb market-wide information in seconds rather than scrolling through tables of numbers.
Reading Colors
The color scale is intuitive:
- Bright green — Strong gains (typically +2% or more)
- Light green — Modest gains (+0.5% to +2%)
- Gray/neutral — Flat (around 0%)
- Light red — Modest losses (-0.5% to -2%)
- Bright red — Strong losses (-2% or more)
Color intensity tells you the magnitude. A stock that's up 5% will be significantly brighter green than one up 0.5%.
Size Modes
ChartBrain offers three size modes, each telling a different story:
Change Mode (Default)
Rectangles are sized by the absolute value of the percentage change. Stocks with the biggest moves — up or down — get the largest tiles. This mode highlights volatility and momentum.
Use when: You want to find the day's biggest movers at a glance.
Market Cap Mode
Rectangles are sized by market capitalization. Apple, Microsoft, and Nvidia will always have the largest tiles because they're the biggest companies. This mode shows where the money is.
Use when: You want to understand the market's weight distribution and see how large-cap stocks are driving index movement.
Equal Weight Mode
All rectangles are the same size. This removes the size bias and lets you compare performance purely by color.
Use when: You want a fair comparison across all stocks regardless of size, or when looking for overlooked small-cap movers.
Sector Analysis
The heatmap groups stocks by sector (Technology, Healthcare, Financials, etc.). This grouping lets you instantly spot:
- Sector rotation — When one sector is all green while another is all red, money is rotating between them.
- Broad market moves — When most sectors are the same color, the market is moving directionally.
- Divergences — When a single stock in a red sector is green, it's outperforming its peers — worth investigating.
Practical Tips
- Check the heatmap first thing in the morning to get an instant read on pre-market/early session sentiment.
- Look for outliers — a bright green tile in a sea of red (or vice versa) often has a catalyst worth investigating.
- Switch between size modes — what looks normal in market cap mode might reveal interesting patterns in equal weight mode.
- Click through — ChartBrain's heatmap is interactive. Click any ticker to see the pressure gauge, news, and AI analysis.
Try It Yourself
ChartBrain's real-time heatmap updates every 10 seconds during market hours, covering 93 stocks across 11 sectors. Start for free — no credit card required.