Commas and Periods (Full Stops) with Numbers (UK and US)
The Quick AnswerCommas can be used with large numbers to assist the reader. They are placed every three decimal places to the left of the decimal point, which is marked with a period (full stop). For example:
- 123.456,789 (This would be correct in many non-English-speaking countries, such as Germany and France.)
Using Commas with NumbersIn countries like the US, UK, and China, commas are used with large numbers to make them easier to read. A comma is placed every 3 decimal places for numbers larger than 999. The decimal point is shown with a period (full stop). For example:
No Commas to the Right of the Decimal PointThe most common convention is not to use commas to the right of the decimal point. For example:
- 4,567.123,456 (This would be considered unusual.)
Other Conventions for Writing NumbersThe use of commas and periods in numbers is not consistent across the world. Below are the most common conventions:
- 4,567.1 (United Kingdom, United States, China)
- 4.567,1 (This convention is used in most of Europe. It is the convention used by most countries.)
- 4 567,1 and 4 567.1 (The practice of using a space to separate the 1000s is also common.)
Do Not Add Commas to Serial or Reference NumbersDo not put your own commas in serial numbers, reference numbers, or 4-figure years. For example:
- According to the document with reference number 912345, serial number 1654880 was destroyed in 1984.
- The film is set in 10,000 BC.