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Commas and Periods (Full Stops) with Numbers (UK and US)
The Quick Answer
Commas 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
- 123.456,789 (This would be correct in many non-English-speaking countries, such as Germany and France.)


Using Commas with Numbers
In 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:- 1,234
- 23,566
- 1,234,967
- 8,000
- 8,000.01
- 8,000.0123456
No Commas to the Right of the Decimal Point
The most common convention is not to use commas to the right of the decimal point. For example:- 4,567.123456
- 4,567.123,456
Other Conventions for Writing Numbers
The 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 Numbers
Do 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.
Interactive Exercise
Here are three randomly selected questions from a larger exercise, which can be edited, printed to create an exercise worksheet, or sent via email to friends or students.- Do you disagree with something on this page?
- Did you spot a typo?