Aviation · FAA AIM 2-3-3
Runway number from heading, nearest tenth.
Enter the magnetic heading of the runway centerline. The runway number is that heading divided by ten, rounded to the nearest whole number.
Inputs
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Runway number
The FAA rule
The Aeronautical Information Manual, paragraph 2-3-3, says that "the runway number is the whole number nearest one-tenth the magnetic azimuth of the centerline of the runway, measured clockwise from the magnetic north", and that numbers and letters are "determined from the approach direction". The letters L, R and C separate parallel runways: L and R for two parallel runways, L, C and R for three.
How to calculate it
- Divide the magnetic heading by 10.
- Round to the nearest whole number.
- If the result is 0, use 36. Single digits get a leading zero, so 9 becomes 09.
- The opposite end differs by 18: add or subtract 18 from the number.
Examples
| Heading | This end | Opposite end |
|---|---|---|
| 274 | 27 | 09 |
| 358 | 36 | 18 |
| 004 | 36 | 18 |
| 090 | 09 | 27 |
| 182 | 18 | 36 |
Headings that end in 5
A heading such as 275 is exactly halfway between 27 and 28. The AIM wording does not say which way to round, so this calculator shows both possible numbers and the matching opposite ends. The number painted on a real runway is the one assigned by the airport and the FAA, so use FAA airport data for any specific runway.
Limits
This is a conversion of a heading you supply, not a lookup of a real runway. Use the FAA airport data for the published designator of any specific runway.
FAQ
How are runway numbers determined?
By the whole number nearest one-tenth the magnetic azimuth of the runway centerline, measured clockwise from magnetic north.
Why is there no runway 00?
A heading near north rounds to 36. The calculator uses 36 when the rounding result is 0.
How do I find the opposite end?
Add or subtract 18 from the runway number. Runway 27 is opposite runway 09.
What do L, C and R mean?
They separate parallel runways: L and R for two, L, C and R for three.
Is the heading true or magnetic?
Magnetic. The AIM measures the centerline azimuth clockwise from magnetic north.
Does a heading ending in 5 round up or down?
The AIM does not say. This page shows both candidates.
Sources
Retrieved 2026-11-02. Statute and regulation text read through the eCFR API (current as of 2026-10-29) or the publisher URLs below.
- FAA, Aeronautical Information Manual, Chapter 2, Section 3: Airport Marking Aids and Signs (runway designators): Runway numbers and letters definition.
Not legal advice or flight instruction
This page summarizes federal aviation rules for general information. It is not legal advice or flight instruction and does not replace the regulation, an instructor, or the FAA. Check the current rule and your own certificate privileges before you fly. Everything runs in your browser; nothing you enter is sent anywhere.