money

Create, calculate and format money in 👑 Nim language.

nimble install money

API reference

Nim library to make working with money safer, easier and fun!

If I had a dime for every time I've seen someone use FLOAT to store currency, I'd have $999.997634 -- Bill Karwin

😍 Key Features

• Framework agnostic
• Works with BigInts via pkg/bigints
• Math Operations +, -, *, /
• Math Operations (mutable) +=, -=, *=, /= => add, sub, multi, div
• Money Formatting
• Money Exchange using 3rd party providers

Examples

[!NOTE] Use compile-time flag -d:moneyDefaultCurrency to change the default currency used by constructors that don't specify a currency. For example, amount(1000) will create a Money instance with the default currency set by the flag. If the flag is not set, it defaults to EUR.

Constructors and formatting

All constructors return a Money instance, which can be formatted using the $ operator. The formatting is based on the currency's symbol and the amount, with two decimal places for cents.

import money

let a = amount(1234, EUR)
let b = 1234.EUR
let c = fmt("4500", USD)

assert $a == "EUR 12.34"
assert $b == "EUR 12.34"
assert $c == "USD 45.00"

Arithmetic

Allows addition, subtraction, multiplication and division of money amounts. The result is always a new Money instance, so the original values remain unchanged. Mutable versions of these operations are also available, which modify the original instance instead of creating a new one.

import money

var a = amount(1000, EUR)  # EUR 10.00
let b = amount(250, EUR)   # EUR 2.50

assert $(a + b) == "EUR 12.50"
a += b
a -= amount(100, EUR)
assert $a == "EUR 11.50"

assert $(amount(129, EUR) * 1.83) == "EUR 2.36"
assert $(amount(1000, EUR) div 4) == "EUR 2.50"

Allocation

Money instances are immutable by default, but mutable versions can be created using var and the mutable operators. This allows for efficient memory usage when performing multiple operations on the same instance.

import money

var x = amount(1000, EUR)
let parts = allocate(x, [50, 30, 20]) # successive ratios

assert $parts[0] == "EUR 5.00"
assert $parts[1] == "EUR 1.50"
assert $parts[2] == "EUR 0.70"

Exchange

Money can be exchanged between different currencies using exchange rates. The library provides a way to perform currency exchange using 3rd party providers, allowing for up-to-date exchange rates.

import std/json
import money

var prevRates = MoneyConversionRates()
prevRates.add(EUR, parseJson("""{"EUR":1,"USD":1.08,"GBP":0.855}"""))
prevRates.add(GBP, parseJson("""{"GBP":1,"EUR":1.17,"USD":1.26}"""))
prevRates.add(USD, parseJson("""{"USD":1,"EUR":0.927,"GBP":0.791}"""))

let eur = amount(2000, EUR)
assert $eur.convert(USD, prevRates) == "USD 21.60"
assert $eur.convert(GBP, prevRates) == "GBP 17.10"

[!NOTE] Check the tests for more examples!

❤ Contributions & Support

• 🐛 Found a bug? Create a new Issue
• 👋 Wanna help? Fork it!
• 😎 Get €20 in cloud credits from Hetzner

This library is inspired from moneyphp/money.

🎩 License

MIT license. Made by Humans from OpenPeeps
Copyright © 2026 OpenPeeps & Contributors — All rights reserved.