Currency Formatting by Locale with Intl.NumberFormat

Currency Formatting Across Locales

Currency formatting is one of the most important uses of Intl.NumberFormat. The position of the currency symbol, the number of decimal places, and the grouping style all vary by locale.

Basic Currency Formatting

const amount = 1234.5;

new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' })
  .format(amount);  // "$1,234.50"

new Intl.NumberFormat('ja-JP', { style: 'currency', currency: 'JPY' })
  .format(amount);  // "¥1,235" (no decimals for yen)

new Intl.NumberFormat('de-DE', { style: 'currency', currency: 'EUR' })
  .format(amount);  // "1.234,50 €"

new Intl.NumberFormat('ar-SA', { style: 'currency', currency: 'SAR' })
  .format(amount);  // "‏١٬٢٣٤٫٥٠ ر.س.‏"

Currency Display Options

The currencyDisplay option controls how the currency is represented:

const opts = { style: 'currency', currency: 'USD' };

// "symbol" (default): "$1,234.50"
// "narrowSymbol": "$1,234.50" (uses narrow symbol when available)
// "code": "USD 1,234.50"
// "name": "1,234.50 US dollars"

Locale-Specific Conventions

Important differences across locales:

• Symbol position: Before the number (en-US: $100) or after (de-DE: 100 €)
• Decimal digits: JPY has 0, most currencies have 2, BHD has 3
• Negative amounts: (USD 100) vs -$100 vs -100 $
• Grouping: Indian rupees use lakh grouping (1,23,456.00)

The currencySign Option

new Intl.NumberFormat('en-US', {
  style: 'currency',
  currency: 'USD',
  currencySign: 'accounting',
}).format(-1234.5);  // "($1,234.50)" instead of "-$1,234.50"

The accounting sign wraps negative amounts in parentheses, which is the standard in financial reporting.