NumberF

Number formatting, currency, and financial math for Elixir.
One zero-config dependency for the numeric work every app ends up rewriting.

NumberF is an Elixir library that handles the numeric chores that show up in almost every real application: formatting money, printing amounts in words on an invoice, working out loan repayments, applying VAT, and displaying numbers the way a user's locale expects them.

It has one runtime dependency (decimal), needs no configuration, and every function is callable directly off the top-level NumberF module.

NumberF.currency(1234.567, "USD")                    # => "USD 1,234.57"
NumberF.to_words(42.75, "Dollars", "Cents")          # => "Forty Two Dollars And Seventy Five Cents"
NumberF.format_currency(1234.56, "fr-FR")            # => "1 234,56 €"
NumberF.calculate_emi(100_000, 0.10, 12)             # => 8791.59
NumberF.calculate_vat(100, 0.2)                      # => %{net: 100.0, vat: 20.0, gross: 120.0}
NumberF.standard_deviation([2, 4, 4, 4, 5, 5, 7, 9]) # => 2.0

Installation

Add number_f to your dependencies in mix.exs:

def deps do
  [
    {:number_f, "~> 0.3.0"}
  ]
end

Then fetch it:

mix deps.get

Requires Elixir 1.14 or later. No application configuration is needed.

What it does

Plus number theory and base conversion: fibonacci/1, prime_factors/1, divisors/1, digital_root/1, to_base/2 and from_base/2 for any base from 2 to 36.

260+ functions, all reachable from the single NumberF module, grouped in the docs by area. Full API reference: hexdocs.pm/number_f

Common tasks

NumberF.currency(1234.567)             # => "ZMW 1,234.57"  (default unit)
NumberF.currency(1234.567, "USD")      # => "USD 1,234.57"
NumberF.currency(1234.567, "USD", 0)   # => "USD 1,235"

# Locale-aware, with the correct symbol and placement:
NumberF.format_currency(1234.56, "en-US")   # => "$1,234.56"
NumberF.format_currency(1234.56, "fr-FR")   # => "1 234,56 €"
NumberF.format_currency(1234.56, "de-DE")   # => "1.234,56 €"

NumberF.to_words(42)                          # => "Forty Two Kwacha"
NumberF.to_words(42.75, "Dollars", "Cents")   # => "Forty Two Dollars And Seventy Five Cents"
NumberF.spell_number(42, "fr")                # => "Quarante-deux"

NumberF.simple_interest(1000, 0.05, 2)        # => 100.0
NumberF.compound_interest(1000, 0.05, 2)      # => 102.5
NumberF.compound_interest(1000, 0.05, 2, 12)  # => 104.94   (monthly compounding)
NumberF.calculate_emi(100_000, 0.10, 12)      # => 8791.59  (principal, annual rate, months)

NumberF.calculate_vat(100, 0.2)                # => %{net: 100.0, vat: 20.0, gross: 120.0}
NumberF.calculate_vat(120, 0.2, true)          # VAT-inclusive: extracts the tax from the gross
NumberF.Tax.calculate_income_tax(75_000, brackets)
# => %{tax: 12248.5, effective_rate: 0.1633}   (progressive brackets)

NumberF.format_number(1234567.89, "en-US")   # => "1,234,567.89"
NumberF.format_number(1234567.89, "fr-FR")   # => "1 234 567,89"
NumberF.format_number(1234567.89, "de-DE")   # => "1.234.567,89"

How it compares

NumberF is a breadth-first utility belt, not a specialist library. Reach for it when you want one small dependency covering many numeric needs; reach elsewhere when you need depth in a single area:

• ex_cldr — full Unicode CLDR data, the right choice when locale correctness across hundreds of locales is a hard requirement.
• money / ex_money — a dedicated Money type with currency-safe arithmetic. Use these if money is a first-class domain type in your system.
• number — a focused port of Rails' number helpers.

NumberF overlaps with all three at the edges, but bundles formatting, finance, tax, statistics, validation, and unit conversion behind a single flat API.

Documentation

• Getting Started
• Cheatsheet — every function on one page
• Currency Formatting
• Financial Calculations
• Internationalization
• FAQ
• Changelog

For AI assistants and LLM tooling

The documentation is published in an LLM-readable form at hexdocs.pm/number_f/llms.txt, following the llms.txt convention. Point Claude, ChatGPT, Cursor, or any retrieval tool at that URL for a complete, plain-text API reference. A condensed llms.txt also lives at the root of this repository.

Contributing

Issues and pull requests are welcome. See CONTRIBUTING.md for the development workflow, and SECURITY.md for reporting vulnerabilities.

git clone https://github.com/jamesnjovu/elixir_number_functions.git
cd elixir_number_functions
mix deps.get
mix test

License

Released under the MIT License. Copyright © 2024-2026 James Njovu.