# General Translation Platform: formatNum
URL: https://generaltranslation.com/en-US/docs/platform/core/reference/gt-class-methods/formatting/format-num.mdx
Docs index: https://generaltranslation.com/llms.txt
Description: Format numbers, currency, percentages, and numeric values by locale. API reference for formatNum.

Formats a number according to locale-specific conventions on a [GT](/docs/platform/core/reference/gt-class/constructor) instance. General Translation uses the built-in `Intl.NumberFormat` API to handle decimal separators, grouping separators, and numbering systems automatically for the target locale.

## Overview [#overview]

Call `formatNum` on a [`GT`](/docs/platform/core/reference/gt-class/constructor) instance with the number to format and an optional options object. It returns the formatted number as a string.

```typescript
const gt = new GT({ targetLocale: 'de' });

const formatted = gt.formatNum(1234.56, {
  style: 'decimal',
  minimumFractionDigits: 2,
});
// "1.234,56" (German number formatting)
```

Signature:

```typescript
formatNum(
  number: number,
  options?: { locales?: string | string[] } & Intl.NumberFormatOptions
): string
```

*Note: `formatNum` runs locally using `Intl.NumberFormat` and does not require an API key. By default it formats for the instance's target locale, falling back to the source locale and then the library default (`en`); pass `locales` to override. For formatting without a `GT` instance, see the standalone [`formatNum`](/docs/platform/core/reference/utility-functions/formatting/format-num).*

## How it works [#how-it-works]

- **Locale resolution.** By default the method formats for the instance's target locale, falling back to the source locale and then the library default (`en`) — not the `locales` config array. Pass `locales` in the options to override for a single call.
- **Intl-backed.** Formatting is delegated to the browser-native [`Intl.NumberFormat`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat), so all standard `Intl.NumberFormatOptions` are supported and locale conventions are applied automatically.
- **Style requirements.** Currency formatting requires both `style: 'currency'` and a valid `currency` code. Unit formatting requires both `style: 'unit'` and a valid `unit` identifier.

## Parameters [#parameters]

| Parameter | Description | Type | Optional | Default |
| --- | --- | --- | --- | --- |
| [`number`](#number) | The number to format. | `number` | No | — |
| [`options`](#options) | Formatting configuration, extending `Intl.NumberFormatOptions` with a `locales` override. | `object` | Yes | — |

### `number` [#number]

**Type** `number` · **Required**

The number to format.

### `options` [#options]

**Type** `{ locales?: string | string[] } & Intl.NumberFormatOptions` · **Optional**

Formatting configuration. The table lists common options exposed by the published Core types and their effective Core defaults. (See the [`Intl.NumberFormat` constructor options](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/NumberFormat/NumberFormat#options) for supplemental standard and runtime-specific details).

| Name | Description | Type | Optional | Default |
| --- | --- | --- | --- | --- |
| `locales` | Override locales for formatting. | `string \| string[]` | Yes | `targetLocale` → `sourceLocale` → `en` |
| `localeMatcher` | Locale matching algorithm. | `'lookup' \| 'best fit'` | Yes | `'best fit'` |
| `numberingSystem` | Numbering system, such as `latn` or `arab`. | `string` | Yes | `'latn'` |
| `style` | Number formatting style. | `'decimal' \| 'currency' \| 'percent' \| 'unit'` | Yes | `'decimal'` |
| `currency` | Currency code (required when `style` is `'currency'`). | `string` | Yes | — |
| `currencyDisplay` | How to display the currency. | `'symbol' \| 'narrowSymbol' \| 'code' \| 'name'` | Yes | `'symbol'` |
| `currencySign` | Currency sign to use. | `'standard' \| 'accounting'` | Yes | `'standard'` |
| `unit` | Unit identifier (required when `style` is `'unit'`). | `string` | Yes | — |
| `unitDisplay` | How to display the unit. | `'short' \| 'narrow' \| 'long'` | Yes | `'short'` |
| `minimumIntegerDigits` | Minimum number of integer digits (1–21). | `number` | Yes | `1` |
| `minimumFractionDigits` | Minimum fraction digits (0–100). The style affects the default. | `number` | Yes | `0` for decimal/percent; currency minor-unit digits for currency; `0` with compact defaults |
| `maximumFractionDigits` | Maximum fraction digits (0–100). The style and minimum affect the default. | `number` | Yes | `3` for decimal; `0` for percent; currency minor-unit digits for currency; `0` with compact defaults |
| `minimumSignificantDigits` | Minimum significant digits (1–21), when significant-digit rounding is active. | `number` | Yes | `1` |
| `maximumSignificantDigits` | Maximum significant digits (1–21), when significant-digit rounding is active. | `number` | Yes | `21`; `2` with compact defaults |
| `roundingPriority` | How fraction- and significant-digit settings interact. | `'auto' \| 'morePrecision' \| 'lessPrecision'` | Yes | `'auto'`; `'morePrecision'` with compact defaults |
| `notation` | Number notation format. | `'standard' \| 'scientific' \| 'engineering' \| 'compact'` | Yes | `'standard'` |
| `compactDisplay` | Compact notation display style. | `'short' \| 'long'` | Yes | `'short'` |
| `useGrouping` | Whether and when to use grouping separators. | `boolean \| 'always' \| 'auto' \| 'min2'` | Yes | `'auto'`; `'min2'` with compact notation |
| `signDisplay` | When to display the sign. | `'auto' \| 'never' \| 'always' \| 'exceptZero' \| 'negative'` | Yes | `'auto'` |
| `roundingMode` | Rounding mode. | `'ceil' \| 'floor' \| 'expand' \| 'trunc' \| 'halfCeil' \| 'halfFloor' \| 'halfExpand' \| 'halfTrunc' \| 'halfEven'` | Yes | `'halfExpand'` |
| `roundingIncrement` | Rounding increment. Non-default values require equal effective minimum and maximum fraction digits and cannot be combined with significant-digit rounding or a non-`'auto'` `roundingPriority`. | `1 \| 2 \| 5 \| 10 \| 20 \| 25 \| 50 \| 100 \| 200 \| 250 \| 500 \| 1000 \| 2000 \| 2500 \| 5000` | Yes | `1` |
| `trailingZeroDisplay` | Whether to display trailing zeros. | `'auto' \| 'stripIfInteger'` | Yes | `'auto'` |

When `notation: 'compact'` is set without any fraction- or significant-digit option, the effective digit defaults are `minimumFractionDigits: 0`, `maximumFractionDigits: 0`, `minimumSignificantDigits: 1`, and `maximumSignificantDigits: 2`. In that case, `roundingPriority` defaults to `'morePrecision'` and `useGrouping` defaults to `'min2'`.

## Returns [#returns]

**Type** `string`

The formatted number, following the target locale's conventions.

## Examples [#examples]

```typescript
import { GT } from 'generaltranslation';

const gt = new GT({ targetLocale: 'en-US' });

// Basic decimal formatting
console.log(gt.formatNum(1234.567));
// Output: "1,234.567"

// German locale formatting
console.log(gt.formatNum(1234.567, { locales: 'de-DE' }));
// Output: "1.234,567"

// French locale formatting
console.log(gt.formatNum(1234.567, { locales: 'fr-FR' }));
// Output: "1 234,567"
```

```typescript
// Currency formatting

// US Dollar formatting
console.log(gt.formatNum(1234.56, {
  style: 'currency',
  currency: 'USD',
}));
// Output: "$1,234.56"

// Euro formatting with German locale
console.log(gt.formatNum(1234.56, {
  style: 'currency',
  currency: 'EUR',
  locales: 'de-DE',
}));
// Output: "1.234,56 €"

// Currency display options
console.log(gt.formatNum(1234.56, {
  style: 'currency',
  currency: 'USD',
  currencyDisplay: 'code',
}));
// Output: "USD 1,234.56"

// Accounting format (parentheses for negative)
console.log(gt.formatNum(-1234.56, {
  style: 'currency',
  currency: 'USD',
  currencySign: 'accounting',
}));
// Output: "($1,234.56)"
```

```typescript
// Percentage and scientific notation

// Basic percentage
console.log(gt.formatNum(0.1234, { style: 'percent' }));
// Output: "12%"

// Percentage with decimal places
console.log(gt.formatNum(0.1234, {
  style: 'percent',
  minimumFractionDigits: 1,
  maximumFractionDigits: 2,
}));
// Output: "12.34%"

// Compact notation
console.log(gt.formatNum(1234567, { notation: 'compact' }));
// Output: "1.2M"

// Scientific notation
console.log(gt.formatNum(1234567, { notation: 'scientific' }));
// Output: "1.235E6"
```

## Notes [#notes]

- Number formatting follows locale-specific conventions automatically.
- The method uses browser-native `Intl.NumberFormat` for performance and accuracy.
- Currency formatting requires both `style: 'currency'` and a valid `currency` code.
- Unit formatting requires both `style: 'unit'` and a valid `unit` identifier.

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