Unit Formatting with Intl.NumberFormat (Meters, Liters, Bytes)

Formatting Units with Intl.NumberFormat

The unit style in Intl.NumberFormat formats values with locale-appropriate unit labels. It supports physical measurements, digital storage, speed, temperature, and more.

Basic Unit Formatting

new Intl.NumberFormat('en-US', {
  style: 'unit', unit: 'kilometer', unitDisplay: 'long',
}).format(42);  // "42 kilometers"

new Intl.NumberFormat('de-DE', {
  style: 'unit', unit: 'kilometer', unitDisplay: 'long',
}).format(42);  // "42 Kilometer"

new Intl.NumberFormat('ja-JP', {
  style: 'unit', unit: 'kilometer', unitDisplay: 'long',
}).format(42);  // "42 キロメートル"

Unit Display Modes

The unitDisplay option controls the label format:

const opts = { style: 'unit', unit: 'liter' };

// "long":   "3.5 liters"
// "short":  "3.5 L"
// "narrow": "3.5L"

Supported Unit Identifiers

Common units include:

• Length: meter, kilometer, centimeter, millimeter, mile, yard, foot, inch
• Mass: kilogram, gram, milligram, pound, ounce
• Volume: liter, milliliter, gallon, fluid-ounce
• Temperature: celsius, fahrenheit
• Speed: kilometer-per-hour, mile-per-hour, meter-per-second
• Digital: byte, kilobyte, megabyte, gigabyte, terabyte
• Duration: year, month, week, day, hour, minute, second

Compound Units

You can combine two units with -per-:

new Intl.NumberFormat('en-US', {
  style: 'unit',
  unit: 'liter-per-100-kilometer',
  unitDisplay: 'long',
}).format(5.8);  // "5.8 liters per 100 kilometers"

new Intl.NumberFormat('en-US', {
  style: 'unit',
  unit: 'mile-per-gallon',
  unitDisplay: 'short',
}).format(30);  // "30 mpg"

Combining with Number Options

Unit formatting respects all other Intl.NumberFormat options:

new Intl.NumberFormat('en-US', {
  style: 'unit',
  unit: 'megabyte',
  unitDisplay: 'short',
  notation: 'compact',
}).format(1500);  // "1.5K MB"