Free Online Heatmap Maker
Make a heatmap free online, no signup — paste a rows-by-columns grid of numbers and get a color-coded matrix that reveals patterns, correlations.
Create Your Heatmap Now — It's FreeWhat Is a Heatmap?
What Data You Need for a Heatmap
A matrix of numbers indexed by two categories: one for rows, one for columns, with a numeric value in every cell that maps to a color. Example: rows = regions, columns = product categories, cells = sales — like ["East","Electronics",140], ["East","Toys",25].
When to Use a Heatmap
Where a Heatmap Works Best
- A correlation matrix of variables (sensors, stocks, survey items) to spot which pairs move together at a glance.
- Website traffic by day-of-week (rows) and hour (columns) to find peak visiting windows for staffing or scheduling.
- Sales or KPI performance across regions and product categories to surface strong and weak combinations.
- Cohort retention grids showing the percent of users still active in week 1, 2, 3 after signup.
Heatmap Example: Regional Sales by Product Category
A retailer maps quarterly sales (in $k) across four regions (rows) and four product categories (columns) to see where each region over- or under-performs. Each cell is colored by sales value, so hot cells flag winners and cold cells flag gaps in the lineup.
Sample data: North: Electronics 120, Apparel 45, Home 80, Toys 30 | South: Electronics 95, Apparel 60, Home 70, Toys 50 | East: Electronics 140, Apparel 38, Home 90, Toys 25 | West: Electronics 110, Apparel 52, Home 60, Toys 40
Electronics is the hottest column at $465k total and drives the single warmest cell (East, $140k), while Toys is the coldest category at just $145k and bottoms out at East's $25k — so East should rethink its toy assortment despite leading in electronics.
How to Create a Heatmap Online
- Step 1: Open ChartLoad and select Heatmap from the chart type picker menu
- Step 2: Enter your row labels, column labels, and the corresponding numeric values for each cell
- Step 3: The color scale applies automatically, mapping your value range to a gradient palette
- Step 4: Choose from predefined color schemes such as sequential, diverging, or custom gradients
- Step 5: Add cell value annotations if you want exact numbers displayed within each colored cell
- Step 6: Click Export to download your heatmap as PNG, PDF, or SVG
Heatmap Best Practices & Tips
- Choose a sequential color scale (light to dark) for single-direction data and a diverging scale when a meaningful midpoint exists.
- Add value labels in each cell when the audience needs exact numbers, not just relative color comparisons.
- Order rows and columns logically — by time, hierarchy, or a clustering algorithm — to reveal patterns.
- Keep cell sizes large enough for labels; if the matrix is very large, rely on color alone with hover tooltips.
- Use a heatmap over a table when the pattern across rows and columns is more important than individual cell values.
- Cluster similar rows and columns together using hierarchical clustering to reveal hidden block patterns.
- Use a perceptually uniform color scale like Viridis to ensure fair visual representation across all value ranges.
Common Heatmap Mistakes to Avoid
- Using a rainbow color scale instead of a single sequential gradient — viewers can't tell whether green is higher or lower than orange, so the color stops encoding magnitude.
- Letting one extreme outlier stretch the color range, which washes 90% of cells out to nearly the same shade; clamp the range or use a log/normalized scale so real variation stays visible.
- Plotting a giant grid (e.g. 200x200) where cells shrink to a pixel and the row/column labels that give the colors meaning become unreadable.
- Leaving rows and columns in arbitrary order — sort or cluster them by value, time, or hierarchy so block patterns line up instead of scattering.
Frequently Asked Questions
Is this heatmap maker free?
Yes — it's 100% free with no signup, no watermark, and no limits. Build your heat map in the browser and export it as PNG, SVG, or PDF.
How do I create a heat map online?
Paste or type a grid of row labels, column labels, and a numeric value for each cell. The color scale maps automatically; then pick a palette, optionally show cell numbers, and export. No install needed.
What's the difference between a matrix heatmap and a calendar heatmap?
A matrix heatmap colors any rows-by-columns grid of categories (e.g. region x product). A calendar heatmap arranges cells by date — days as columns or rows across weeks. For day-by-date data, use our calendar heatmap tool instead.
How do I make a heatmap in Excel vs. here?
In Excel you'd apply conditional formatting color scales to a cell range, which is fine for quick checks but hard to share or restyle. This tool gives you proper palettes (sequential, diverging, Viridis), clean labels, and one-click PNG/SVG/PDF export.
Which color scale should I use for a heatmap?
Use a sequential scale (light to dark) for single-direction data like counts, and a diverging scale (two colors meeting at a midpoint) when zero or an average is meaningful, such as correlations or change-versus-baseline.
Related Chart Types
Ready-Made Heatmap Templates
Skip the blank canvas — open a free, editable Heatmap template, swap in your own data, and export. Browse all templates.
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