Heatmap Generator & Heat Map Maker
Paste a table or drop an Excel or CSV file — every cell is binned into an exact color scale by code, and the AI draws a publication-ready heatmap with row and column labels, cell values and a color bar.
Or start from an example
Heatmap color maps
One real render per color map, each from a different dataset — click a card to apply the map, or take its data into the composer.
What is a heatmap?
A heatmap (heat map) shows a table of numbers as a grid of colored cells, one row and one column per label. Color encodes each value, so patterns across rows and columns — gradients, blocks, outliers — read at a glance.
About this heatmap generator
- Paste a table copied from Excel, type it as Columns: … plus one Row: values line per row, or attach a CSV, TSV or Excel file.
- Row labels come from the first column and column labels from the header row; blank or NA cells are drawn as missing.
- Every value is binned by code into five color steps with round boundaries, and the colors are written into the prompt cell by cell.
- Data that crosses zero gets a diverging scale centered on 0 automatically, and “row z-scores” scales each row before binning.
- Grids up to 12 × 12 are accepted; beyond that image models start miscounting cells, so the tool asks you to trim instead of guessing.
How row z-scores are computed
A row z-score says how many standard deviations a cell sits above or below the mean of its own row. Gene expression heatmaps use it so every gene is compared on the same scale, whatever its absolute level.
z = (x − row mean) / row SD
In words
Subtract the row’s mean from each value, then divide by the row’s standard deviation (n − 1 denominator). A z-score of 2 means the value is two standard deviations above that row’s average; the result is centered on 0 and drawn on a diverging scale.
Z-scoring is off by default and values are drawn as given. Write “row z-scores” in the description to turn it on.
How to make a heatmap
Add your table
Paste cells from Excel, type Columns: S1, S2… followed by TP53: 0.95, 0.10… for each row, or attach a CSV or Excel file. The binned grid appears above the box in the exact colors the figure will use.
Choose the color map
Blues for plain magnitudes, viridis for color-blind-safe figures, blue–white–red for values either side of zero, grayscale for black-and-white print. Say “no values” to leave the cells unlabeled.
Generate and refine
The AI paints each cell from the computed bins and never estimates a color. Keep editing in chat — relabel, add a title, switch the map — then export as PNG, SVG or PPTX.
Choosing a color map
The right color map depends on what the numbers mean, not on taste.
| Color map | Type | Use it for | Why |
|---|---|---|---|
| Blues | Sequential | Counts, concentrations, expression from low to high | Darkness rises with the value, so darker always means more |
| Viridis | Sequential, perceptually uniform | Figures that must survive color-vision deficiency and grayscale printing | Equal steps in the data look like equal steps in color |
| Blue–white–red | Diverging | Z-scores, log fold changes, correlations from −1 to 1 | White marks zero and the two hues show direction |
| Grayscale | Sequential | Black-and-white print and photocopies | Readable without any color at all |
| Rainbow (jet) | Avoid | — | Uneven lightness invents boundaries that are not in the data |
| Red–green | Avoid | — | Unreadable with the most common forms of color blindness |
Color-vision deficiency affects about 8% of men and 0.5% of women worldwide, which is why red–green and rainbow scales keep a figure from part of its readership.
Heatmap vs clustered heatmap vs table
A heatmap keeps your rows and columns in the order you give, a clustered heatmap reorders them by similarity and adds dendrograms, and a table shows exact numbers without the pattern.
| Question | Heatmap | Clustered heatmap | Table |
|---|---|---|---|
| Row and column order | As supplied — time, dose or your own order | Reordered by hierarchical clustering | As supplied |
| Shows patterns at a glance | Yes | Yes, grouped by similarity | No |
| Exact values | Printed in the cells when there is room | Rarely — usually too many cells | Always |
| Typical size | A few to a dozen rows and columns | Dozens to thousands of rows | Any size, but hard to scan |
| Made with | This generator | Clustering software such as R pheatmap or seaborn clustermap | A spreadsheet |
This generator draws ordered heatmaps and computes no clustering. If your analysis clustered the rows, paste them in that order and add the dendrogram from the analysis software, where its branch heights are real.
Where heatmaps are used
Heatmaps are used wherever a matrix of values has a pattern worth seeing — across genes, samples, doses or time.
Gene expression
Genes as rows, samples or conditions as columns, often as row z-scores on a diverging scale — the standard summary panel of an RNA-seq or qPCR experiment.
Correlation matrices
Pairwise Pearson or Spearman coefficients from −1 to 1 on a blue–white–red scale, with 1 on the diagonal, to show which variables move together.
Dose–response grids
Viability or synergy across the concentrations of two drugs, where the gradient across the grid is the finding.
Classifier evaluation
Confusion matrices with true classes as rows and predicted classes as columns, and the count printed in each cell.
Heatmap questions, answered
How do I make a heatmap from my data?
Paste the table into the description or attach a CSV or Excel file, pick a color map and generate. Put row labels in the first column and column labels in the first row. The binned grid is shown above the box before any credit is spent.
Can I make a heatmap from Excel?
Yes — attach an .xlsx file, or copy the cells in Excel and paste them straight into the description. The sheet with the most numbers is used, and blank or NA cells are drawn as missing rather than as zero.
How do I make a gene expression heatmap?
Put genes in rows and samples in columns, then pick a map — or write “row z-scores” to scale each gene to its own mean and SD. Z-scored data is drawn on a blue–white–red scale centered on zero, the usual convention for expression panels.
How do I make a correlation heatmap?
Paste the correlation matrix with the same labels on rows and columns. Values that cross zero get a diverging scale from −1 to 1 automatically, with each coefficient printed in its cell. The tool plots coefficients you have computed; it does not compute them from raw data.
Which color map should I use for a heatmap?
Sequential maps (blues, viridis) for values from low to high, a diverging map (blue–white–red) for values either side of a meaningful zero, grayscale for black-and-white print. Avoid rainbow and red–green scales: they distort the data and lose readers with color-vision deficiency.
How big can the heatmap be?
Up to 12 rows and 12 columns. Beyond that, image models start miscounting cells, so the tool refuses a larger table rather than drawing a wrong grid — trim it, aggregate it or split the figure into panels.
Can I hide the numbers in the cells?
Yes — write “no values” or “without numbers” in the description. Values are printed by default, in white on the darker colors and in black on the lighter ones.
Does the heatmap include clustering or a dendrogram?
No — rows and columns keep the order you give, and no clustering is computed. If your analysis clustered them, paste the rows in that order and add the dendrogram from your analysis software.
Why are the colors in steps instead of a smooth gradient?
Because five discrete bins can be drawn exactly — each cell is told its bin and its hex color — while a continuous gradient would leave the AI to guess every shade. The bin boundaries are round numbers printed on the color bar, so each cell’s range stays readable.
Does the AI change or invent my numbers?
No. The bins, colors and printed values are computed by code from your table and written into the prompt cell by cell. Every regeneration recomputes them, so switching the color map never moves a value into the wrong bin.
Is a heat map the same as a heatmap?
Yes — heat map, heatmap and heat-map are spellings of the same chart. Analysis software mostly writes “heatmap”; general writing often uses “heat map”.
Is this heatmap generator free?
Yes to start — every new account gets 100 free credits and no card is required to sign up. Previewing the binned grid costs nothing; credits are spent only when you generate the figure. Search for a heat map generator, a heatmap creator or a heatmap maker and you land on the same thing: a table in, an exact colour-binned grid out.
Sources
- Heat maps (Points of View) — Nature Methods
- The misuse of colour in science communication — Nature Communications
Keep exploring
Our other diagram tools, and the guides behind them.
Tools
Draw your heatmap
From a pasted table to a publication-ready figure in about a minute — colors binned exactly, styling handled by the AI.
Start drawing