Radiotelephony – Numbers

Updated on 5th March, 2017

Helicopter Radiotelephony

Pronouncing Numbers

During a recent flight I was cleared by ATC to climb to “fifteen hundred” feet. If you are an aviator, you should be aware that the number “fifteen” is never used in standard radiotelephony. I decided to make this post to let you know how to transmit numbers  when using the radio.

Transmission of numbers is frequently done incorrectly and this post should make you confident in how to do it.

Transmission of Numbers

Numeral                Pronunciation

0                              Zero                              Bold Text shows correct pronounciation

1                               One

2                               Two

3                               Tree

4                               Four

5                               Fife

6                               Six

7                               Seven

8                               Eight

9                               Niner

Decimal                  Decimal

Hundred                 Hundred

Thousand               Tousand


Almost every number transmitted to you by ATC must be repeated back (with some exceptions).

All numbers (with a few exceptions listed below) must be transmitted by pronouncing each digit separately.

Check out a preview of my New RADIOTELEPHONY Book HERE

General Numbers

When transmitting messages containing aircraft callsigns, altimeter settings, flight levels (with the exception of FL 100, 200, 300 etc. which are expressed at ‘Flight Level (number) HUNDRED’), headings, wind speeds/directions, pressure settings, transponder codes and frequencies, each digit shall be transmitted separately; examples of this are as follows:

Type                       Number                  Transmitted as

Aircraft Reg.              N3456S                    November Tree Four Fife Six Sierra

Flight Level                FL 100                     Flight Level One Hundred

Flight Level                FL 130                     Flight Level One Tree Zero

Heading                     130 Degrees            One Tree Zero Degrees

Speed                         85 Knots                  Eight Fife Knots

Frequency                  121.85                      One Two One Decimal Eight Fife

Squawk                       0234                        Zero Two Tree Four

Altitude, Height and Visibility

All numbers used in the transmission of altitude, height, cloud height, visibility and runway visual range which contain whole hundreds and whole thousands should be transmitted by pronouncing each digit in the number of hundreds or thousands followed by the word HUNDRED or TOUSAND as appropriate. Combinations of thousands and whole hundreds shall be transmitted by pronouncing each digit in the number of thousands followed by the word THOUSAND and the number of hundreds followed by the word HUNDRED; examples of this convention are as follows:

Number               Transmitted as

10                               One Zero

100                             One Hundred

2,300                          Two Tousand Tree Hundred

12,000                        One Two Tousand

22,000                        Two Two Tousand

NOTE: Decimal points are NEVER pronounced as “point”. ALWAYS as “decimal”.


When transmitting time, only the minutes of the hour are normally required. However, the hour should be included if there is any possibility of confusion. Time checks must be given to the nearest minute. Co-ordinated Universal Time (UTC) MUST be used at all times, unless specified. 2400 hours designates midnight, the end of the day, and 0000 hours the beginning of the day.

Number                 Transmitted as

0923 Hours              Time Two Tree OR Time Zero Niner Two Tree

1400 Hours              Time One Four Zero Zero

1743 Hours               Time Four Tree OR Time One Seven Four Tree



If you study this post carefully, you should have no problem pronouncing numbers correctly on the radio. You will occasionally hear other pilots and Air Traffic Controllers pronounce numbers incorrectly. They are wrong. You will know that they are wrong. You will make mistakes – just like me. Put your mistakes behind you and strive to keep a high standard. Remember – “Practice makes perfect”.

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