CH3 File

What are CH3 files and how to open them

Are you having problems opening a CH3 file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your CH3 files.

What is a CH3 file?

A .CH3 file is a Harvard Graphics Chart file.

Harvard Graphics Chart files are binary chart-graphics files created by Harvard Graphics version 3.x (a DOS/early Windows presentation/charting program). They are used to store individual charts - complete with their numerical data, axes settings, labels, colours, and layout instructions - that were built inside Harvard Graphics for use in presentations or printed output. Their purpose is to retain all chart design and data so that the chart can be edited, formatted, or rendered consistently by the software.

They are written by Harvard Graphics (version 3.x), often when a user saves a chart object or document built in that program. Once created, they are typically loaded back into Harvard Graphics when editing or displaying the chart in a presentation. Other programs may import or view them, though edit support and fidelity vary.

Internally, these files begin with the 4 ASCII bytes "HGB3" at position zero, which stands for Harvard Graphics Binary version 3. This signature identifies version 3.x chart files. Other internal identifiers describe chart data blocks, formatting flags, and layout records (axes, labels, colour tables), though full technical structure is proprietary.

How to open CH3 files

Important: Different programs may use files with the CH3 file extension for different purposes, so unless you are sure which format your CH3 file is, you may need to try a few different programs.

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: August 31, 2026

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