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Commas and Periods (Full Stops) in Numbers
(UK and US)
Commas in Numbers
Commas can be used with large numbers to assist the reader. They are placed every three digit positions 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 in Numbers (US, UK, and China)
In the US, UK, and China, a comma is placed every 3 digit positions 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
billions |
, (comma) |
hundred millions |
ten millions |
millions |
, (comma) |
hundred thousands |
ten thousands |
thousands |
, (comma) |
hundreds |
tens |
units |
. (point) |
tenths |
hundredths |
thousandths |
ten thousandths |
hundred thousandths |
millionths |
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.)
billions |
. (point) |
hundred millions |
ten millions |
millions |
. (point) |
hundred thousands |
ten thousands |
thousands |
. (point) |
hundreds |
tens |
units |
, (comma) |
tenths |
hundredths |
thousandths |
ten thousandths |
hundred thousandths |
millionths |
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.
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