How to Make a Heatmap from a Table (Free Online)

To make a heatmap, open the Heatmap Maker and paste a block of cells from Excel or Google Sheets — column labels in the first row, row labels in the first column, numbers in between. Each cell is coloured by its value, so patterns jump out. Choose a Colour scale, show the values in the cells, and download a PNG, JPG or SVG.

Make a heatmap step by step

1. Open the Heatmap Maker.
2. Paste or type the Table:

Day,9am,12pm,3pm,6pm
Mon,12,40,25,18
Tue,15,42,28,20
Wed,14,55,30,22
Thu,18,48,35,30
Fri,22,60,45,52

1. Choose the Colour scale — Blues, Greens, Reds, Viridis, Heat, or Red – white – blue (diverging).
2. For a diverging scale, set the Middle value (0 by default).
3. Tick Show values in cells, set the Decimals and a Unit, and adjust the Cell gap and Colour legend.
4. Download PNG, SVG or JPG.

Sequential or diverging?

• Sequential scales (Blues, Greens, Heat, Viridis) go from low to high — for counts, sales, visitors, temperatures.
• Diverging scales (red – white – blue) have a meaningful middle — for profit and loss, change versus last year, survey scores around neutral, or correlations from −1 to 1. Set the Middle value to the neutral point.

Viridis is designed to be readable for colour-blind viewers and when printed in grey.

Heatmap ideas

• Busiest hours of the week — days × hours, from bookings, website visits or support tickets.
• Sales by region and month.
• Correlation matrices — how strongly variables move together (−1 to 1, diverging scale).
• Attendance or habits — people × weeks.
• Exam results — students × questions, to find questions everyone struggled with.
• Product feature comparisons — scores per feature.

Missing data stays honest

Empty cells are drawn grey, so missing data is never mistaken for zero. Text in each cell switches between dark and white automatically for contrast.

Tips for readable heatmaps

• Order rows and columns meaningfully — days in order, regions by size — so patterns form blocks rather than noise.
• Show values when exact numbers matter; hide them for a cleaner overview of large tables.
• Round sensibly with Decimals — two decimals in every cell is hard to read.
• Watch extreme values: one huge number can wash out the colours of all the others. Consider showing it separately.

A worked example: busiest hours

Export support tickets per day and hour from your help desk as a table — days down the side, hours across the top — and paste it in with the Heat scale. The darkest block shows when the team is most needed (perhaps Monday mornings and Friday afternoons), which is exactly the information a staffing plan needs. Turn on Show values in cells for the exact counts.

Correlation matrices

For a table of correlations between variables (−1 to 1), choose Red – white – blue (diverging) and keep the Middle value at 0. Strong positive correlations turn deep blue, strong negative ones deep red, and weak ones fade to white — the important relationships stand out immediately.

Related charts

• Comparing a single row or column? A bar chart shows exact differences better.
• Showing parts of a whole by size? Try a treemap.

Privacy

Your table stays in your browser — nothing is uploaded or stored.

Frequently asked questions

How big can the table be?

Dozens of rows and columns work well; for very large tables, make the image bigger in the style settings.

Can I paste from Google Sheets?

Yes — select the block including labels, copy, and paste.

Can I change the colours?

Choose another Colour scale; diverging scales centre on the Middle value you set.