calculator-helper

A simple skill that performs mathematical calculations, unit conversions, and numeric computations.

What This Example Teaches

• Creating a computational skill
• Formatting mathematical output clearly
• Showing step-by-step working
• Using read-only tools (no file modifications needed)

How to Use

1. Install the Skill

# Copy to your Claude config
cp SKILL.md ~/.claude/skills/calculator-helper.md

# Or for project-specific
cp SKILL.md your-project/.claude/skills/calculator-helper.md

2. Try It Out

cd your-project
claude

# Then ask:
"Calculate 25% of 1500"
"Convert 75 Fahrenheit to Celsius"
"What's 145 * 23?"
"If I invest $1000 at 5% for 3 years compound, what do I get?"

3. Watch It Activate

The skill automatically activates when you mention:

• "calculate"
• "compute"
• "convert"
• "what is the result"
• Any math-related question

Example Usage

You:

I need to calculate a 15% tip on a $67.50 bill

Claude (using calculator-helper skill):

Calculating 15% tip on $67.50:

Tip amount: 67.50 × 0.15 = $10.13
Total bill: 67.50 + 10.13 = $77.63

Answer:
- Tip: $10.13
- Total to pay: $77.63

You:

Convert 100 kilometers to miles

Claude (using calculator-helper skill):

Converting 100 kilometers to miles:

Conversion factor: 1 km = 0.621371 miles

100 km × 0.621371 = 62.1371 miles

Answer: 100 km = 62.14 miles (approximately 62 miles)

What Makes This a Good Beginner Example?

1. Clear, Specific Purpose

• Focused on mathematical computations
• Doesn't try to do file operations or code modifications
• Easy to understand and test

2. Read-Only Operation

allowed-tools: [Read]

• Only needs Read tool (for context if needed)
• Can't modify files or run commands
• Very safe to use

3. Multiple Use Cases

• Arithmetic calculations
• Unit conversions
• Financial calculations
• Percentage calculations
• Scientific computations

4. Shows Working

• Displays step-by-step calculations
• Explains formulas used
• Makes results verifiable

Customization Ideas

Add Business-Specific Calculations

## Company-Specific Formulas

**Gross Margin:**
(Revenue - COGS) / Revenue × 100

**Customer Lifetime Value:**
Average Order Value × Purchase Frequency × Customer Lifespan

Add Domain-Specific Conversions

## Printing Industry Conversions

- 1 point = 1/72 inch
- 1 pica = 12 points = 1/6 inch
- Letter size = 8.5 × 11 inches = 612 × 792 points

Support Your Local Units

## Australian Measurements

- 1 cup = 250ml (vs 236.588ml in US)
- 1 tablespoon = 20ml (vs 15ml in US)
- Metric system preferred

Common Issues

Skill doesn't activate?

Check: Description needs calculation trigger words

# ❌ Too vague
description: Does math

# ✅ Specific with triggers
description: Performs calculations. Use when user asks to "calculate", "compute", or needs math help

Results seem imprecise?

Fix: Specify rounding rules in the skill:

## Rounding Rules

- Money: 2 decimal places
- Percentages: 2 decimal places
- Scientific: 4 significant figures
- Measurements: 2 decimal places

Need more conversion types?

Add: Expand the conversion reference section:

## Data/Digital Conversions

- 1 KB = 1,024 bytes
- 1 MB = 1,024 KB
- 1 GB = 1,024 MB

Tips for Use

For Simple Calculations

Just ask naturally:

• "What's 15% of 200?"
• "Convert 50 miles to km"
• "Calculate 25 * 18"

For Complex Problems

Provide all details:

• "Calculate compound interest on $5000 at 6% annually for 3 years"
• "Scale a recipe from 4 to 9 servings if it needs 2.5 cups flour"

For Conversions

Be specific about units:

• "Convert 100 km to miles" (not just "convert 100")
• "What's 75°F in Celsius?" (specify temperature)

Learning Opportunities

Understand Activation

This skill teaches how descriptions trigger activation:

• Specific keywords ("calculate", "compute")
• Natural language patterns ("what is the result of")
• Context clues (numbers with math operators)

See Tool Restrictions

With only [Read] tool:

• Can read files for context
• Can't modify anything
• Very safe and focused

Practice Clear Output

Learn to format results:

• Show formulas
• Display working
• Provide clear final answers
• Include units

Next Steps

Extend This Skill

• Add statistical calculations (mean, median, mode)
• Support matrix operations
• Add probability calculations
• Include geometry formulas

Create Related Skills

• unit-converter - Focused only on conversions
• financial-calculator - Business-specific calculations
• recipe-scaler - Cooking-specific math

Combine With Other Skills

• Use with comment-generator to document calculation code
• Pair with code review for validating numeric logic
• Integrate with data analysis workflows

Files

• SKILL.md - The skill file (copy this to .claude/skills/)
• README.md - This documentation

Related Examples

• comment-generator - Another read-only, focused skill
• todo-finder - Another analysis-focused skill
• See intermediate examples for domain-specific calculators