General (ICAO)

ICAO Annex 14 Vol I, §5.2.2 governs runway designation. A runway is given a two-digit number 01 to 36 corresponding to the magnetic bearing of the runway direction rounded to the nearest tenth (e.g. magnetic 273° → designator 27, magnetic 268° → 27, magnetic 264° → 26).

Because a runway can be used in both directions, it has two designators differing by 18 (180°) — e.g. 09/27, 04/22, 16/34.

When more than one runway exists in the same direction, a letter suffix is added:

2 parallel runways: L (Left) and R (Right) — e.g. 07L / 07R
3 parallel runways: L / C / R (Left / Center / Right) — e.g. 07L / 07C / 07R
4 or more parallel runways: designators are shifted by 1 (e.g. 06L/06R + 07L/07R)

For a magnetic bearing of 003° the designator 00 is avoided; 36 is used; for 360°, 36 is used (never 00).

Europe (EASA / EU)

ICAO Annex 14 is applied EU-wide via Regulation (EU) 139/2014 (Aerodromes — Part-ADR) and the associated CS-ADR-DSN (Certification Specifications and Guidance Material for the Design of Surface Movement Areas). EASA mandates compliance with the ICAO standards for certified aerodromes; national authorities apply the specifications also to non-certified aerodromes.

Germany (national)

Applied under EU law. When magnetic variation changes significantly, the runway designator may be reassigned — the process is handled by the Luftfahrt-Bundesamt (LBA) and DFS and published in AIP Germany as well as via NfL (Notices to Airmen).