Calculator Helper Skill - Beginner Example

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