CalcMark

Calculations embedded in markdown documents.

CalcMark is a terminal-based calculation notepad. Write your thinking in plain text, add calculations that reference each other, and watch results update as you type.

Unlike spreadsheets, CalcMark files are human-readable, diffable, and live in your terminal.

Installation

macOS/Linux (Homebrew):

brew install calcmark/tap/calcmark

Download binary:

Platform	Download
macOS (Apple Silicon)	calcmark_VERSION_darwin_arm64.tar.gz
macOS (Intel)	calcmark_VERSION_darwin_amd64.tar.gz
Linux (x64)	calcmark_VERSION_linux_amd64.tar.gz
Linux (arm64)	calcmark_VERSION_linux_arm64.tar.gz
Windows (x64)	calcmark_VERSION_windows_amd64.zip

After downloading, extract and move cm to a directory in your PATH. On macOS, you may need to run xattr -d com.apple.quarantine ./cm before first use.

Quick Start

1. Create a file called budget.cm:

# Monthly Budget

income = $5000
rent = $1500
savings_rate = 20%
savings = income * savings_rate
remaining = income - rent - savings

2. Open in the TUI editor:

cm budget.cm

3. Or evaluate from command line:

cm eval budget.cm

4. Or convert to other formats:

cm convert budget.cm --to=html -o budget.html

Examples

Explore example files to see CalcMark in action:

• Budget planning - Monthly budget with income, expenses, savings
• Unit conversion - Converting between units
• Capacity planning - Engineering calculations with constants

Run any example:

cm testdata/examples/budget.cm

Features

• Variables flow downward - Define once, reference anywhere below
• Units are first-class - 5 miles in km, 20 celsius in fahrenheit
• Currencies - $100, 50 EUR, automatic formatting
• Percentages - savings_rate = 20%, then income * savings_rate
• Functions - avg(), sqrt(), capacity(), and more
• YAML front matter - Define document-level constants (exchange, globals, scale, convert_to, measurement, fiscal_year_starts; see spec/document/frontmatter_registry.go for the authoritative list)
• Export formats - Convert to HTML, Markdown, JSON, or plain text

Help Commands

cm help              # General help
cm help functions    # List all functions with descriptions
cm help constants    # List built-in constants
cm convert --help    # Export format options

Press Ctrl+H (or F1) in the TUI editor for keybindings.

Learn More

• Documentation - Complete documentation with examples
• Language Reference - Formal language specification
• CHANGELOG - Release notes and migration guides

Development

Prerequisites:

• Go 1.24+
• Task — task runner (brew install go-task)

Optional (for recording demo GIFs):

• VHS — terminal recorder (brew install vhs)
• VHS requires ttyd and ffmpeg, installed automatically by Homebrew

task test       # Run all tests
task quality    # Lint, vet, staticcheck
task build      # Build the cm binary
task record-demos  # Regenerate all demo GIFs (requires VHS)

License

MIT