How to Make a Heatmap from a Table of Numbers

Published October 11, 2026

Free tool: Heatmap Maker→

A heatmap turns a table of numbers into a grid of colors: the higher the value, the darker the cell. Patterns that are hard to spot in rows of figures, such as the busiest hours of the week or the strongest products in each region, jump out immediately. This guide explains when to use a heatmap, how to set up your data and choose a color scale, and how to make one with the free Heatmap Maker.

When to use a heatmap

Heatmaps work well for tables where both the rows and the columns mean something, for example:

• website visits by day of the week and hour
• sales by product and region
• survey answers by question and group
• monthly figures by year, to compare seasons
• staff availability by person and shift

If you only have one row of values, a bar graph is clearer; heatmaps shine when there's a grid to scan.

Example: website visits by day and time

Here's a week of website visits, counted at six times of day (this is the sample the Heatmap Maker opens with):

As a heatmap, the story is instant: early mornings are pale everywhere, weekday lunchtimes and evenings are dark, and the darkest cell, Friday at 6pm with 190 visits, marks the best time to publish. Weekend mornings are noticeably quieter than weekday ones.

How the colors work

The Heatmap Maker uses a sequential color scale: one color running from light to dark. The smallest value in the table gets the lightest shade, the largest the darkest, and everything else falls in between in proportion. A key under the chart shows which values the lightest and darkest shades stand for. Cells that don't contain a number are shown in gray as no data.

How to make a heatmap with Graph Maker

1. Open the Heatmap Maker.
2. Type a chart title, such as "Website Visits by Day and Time".
3. Enter your table in Data Table: the first row holds the column labels, the first column holds the row labels, and the rest are numbers. Separate the cells with commas, or paste straight from a spreadsheet.
4. Add the axis titles, such as "Time of day" for the columns and "Day" for the rows.
5. Choose a color scale: blue, green, orange, purple, red or a custom color.
6. Decide whether to show the values in the cells, and how many decimal places to use.
7. Set the background, title and font colors, then download the heatmap as a PNG, JPG or SVG.

Hover over any cell to see its row, column and value.

Tips for a clear heatmap

• Order rows and columns logically, such as days in order and hours in order, so patterns line up.
• Show the values when the table is small. Readers then get both the overall picture and the exact numbers.
• Use one color family. A rainbow of colors suggests categories that aren't there and is hard to read in order.
• Compare like with like. If rows have very different scales, such as a big store and a small one, convert to percentages first so one row doesn't swamp the rest.
• Keep labels short so the grid stays compact.

Frequently asked questions

What is a heatmap used for?

Spotting patterns in a table of numbers, such as the busiest times, the strongest and weakest combinations, or seasonal changes, by turning each value into a shade of color.

How do I make a heatmap from a spreadsheet?

Copy the block of cells, including the header row and the row labels, and paste it into the Heatmap Maker's data box. Tab-separated data from a spreadsheet works as well as comma-separated text.

What colors should a heatmap use?

For values that run from low to high, use one color from light to dark. Make sure the darkest and lightest shades are easy to tell apart, and include a key so readers know what the colors mean.