UK number conventions and why they matter
British English uses a comma as the thousands separator and a period as the decimal separator: 1,234,567.89. Currency follows the same pattern: £1,234.56. One subtlety is that many UK style guides treat four-digit numbers as optional for the comma , writing 1234 rather than 1,234 is acceptable in running text. In scientific and technical writing, the ISO 80000 standard recommends a thin space as the thousands separator (1 234 567.89), which you will see in UK academic publications. Phone numbers follow the +44 prefix format for international dialling.
Mixing conventions causes real errors: a French spreadsheet exported with 1 234,56 read into a UK system as two separate values (1 234 and 56) or as the string "1 234,56" rather than the number 1234.56. This tool converts cleanly between all major conventions.
International number format reference
| Locale | Example | Thousands sep. | Decimal sep. |
|---|---|---|---|
| English (US/UK) | 1,234,567.89 | comma | period |
| French / European (ISO) | 1 234 567,89 | space | comma |
| German | 1.234.567,89 | period | comma |
| Swiss German | 1'234'567.89 | apostrophe | period |
| Indian | 12,34,567.89 | comma (groups of 2) | period |
| Spanish (Spain) | 1.234.567,89 | period | comma |
Where formatting errors cause problems
Data imports are the most common failure point. A CSV exported from French accounting software uses commas as decimal separators; the same file opened in Excel on a UK machine may misread every number. Database fields typed as DECIMAL reject non-numeric strings, so a formatted number like "1,234.56" must be stripped to "1234.56" before insertion. Financial reports shared across borders need explicit locale declarations to avoid ambiguity.
Formatting in context: currency, percentages, IBAN
UK currency amounts always place the symbol before the number with no space (£1,234.56). Percentages place the sign after the number (12.5%). For IBAN numbers, the UK NatWest format groups characters in sets of four for readability: GB29 NWBK 6016 1331 9268 19. If you work with international bank transfers, pair this tool with the Currency Converter to convert amounts before formatting them for the destination locale.