# Calculator

> Skill `calc.evaluate` on Faro. Free. 0 sub-skills.

Evaluates arithmetic expressions exactly, converts numbers between bases (binary, hex, decimal, and more), and converts between integers and Roman numerals. Runs locally with no charge and no rounding errors.

**Category:** Developer Tools  
**Tags:** calculator, math, arithmetic, base-conversion, roman-numerals  
**Use when:** You need exact arithmetic, base conversion, or Roman numerals the model should not eyeball.  
**Not for:** Symbolic math, unit conversion (use units), or word problems.  
**Returns:** information

## How to run
Skills run through one gateway with your Faro token. Hand it an `intent` in plain language; Faro routes to the right sub-skill, runs it, and bills per call. Raw tools are internal plumbing and are not directly callable.

```
POST https://skill.askfaro.com/skills/calc.evaluate/run
Authorization: Bearer faro_<your_key>
Content-Type: application/json

{"intent":{"prompt":"What is (15 + 7) * 3 - 4?"}}
```

Or from the CLI:

```bash
pip install askfaro-cli && askfaro auth login
askfaro run calc.evaluate "What is (15 + 7) * 3 - 4?"
```

Full run reference: https://askfaro.com/llms/run.md — Agent recipe: https://askfaro.com/llms/skill.md

## Example requests

- What is (15 + 7) * 3 - 4?
- Convert 255 to hexadecimal
- Convert XLII to a number

## What it can do

- Evaluate an arithmetic expression with + - * / and parentheses.
- Convert a number between bases (2 to 36), e.g. binary, hex, decimal.
- Convert between integers and Roman numerals.

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On the web: https://askfaro.com/search/calc.evaluate