Runway numbers explained: what 25C, 08L and 36 mean at airports

On the radio it’s “cleared to land runway two five centre,” the weather page says “RWY 08L,” and in the spotter forum someone writes that everything is running over the 18 today. To a beginner, it sounds like a secret code. Yet behind every runway designator is a simple logic of compass heading and position. Once you’ve understood it, two digits and a letter tell you where the aircraft are coming from, which runway is in front of your spot and why an old spotter guide suddenly gives different numbers than the signs at the airport.

Runway designators: the short answer

A runway designator consists of a number from 01 to 36 and, for parallel runways, a letter. The number is the runway’s magnetic heading, rounded to the nearest ten degrees and divided by ten. The letter – L, C or R – says whether the runway is on the left, in the middle or on the right from the approaching pilot’s point of view. Every runway has two designators, one for each direction, and the numbers always differ by 18.

From “25C” you can therefore read: the runway points roughly toward 250 degrees, so west-southwest, and it is the middle one of three parallel runways. At the other end, the same runway is called 07C.

The digits: a rounded compass heading

Imagine you’re standing at the start of the runway, looking down the centerline. The magnetic compass heading you’re facing is the basis of the number. It is rounded to the nearest ten, and the last zero is dropped:

• 248 degrees → rounded 250 → runway 25
• 076 degrees → rounded 080 → runway 08
• 226 degrees → rounded 230 → runway 23
• 357 degrees → rounded 360 → runway 36

Three subtleties are worth knowing:

• Leading zero: Under ICAO rules, single-digit numbers are written with a zero in front, so 05 or 08. In US civil aviation that zero is dropped; there it’s Runway 5 or Runway 8. The same thing is meant.
• No 00: A runway pointing north is 36, not 00. Its reciprocal is 18.
• Digits are spoken one by one: On the radio, each digit is spoken separately – “two five,” not “twenty-five.” That way numbers can’t be confused even with poor reception. If you listen in, pay attention to the legal situation; the post Listening to air traffic radio sums it up.

Because the number refers to magnetic north, it deviates slightly from the true direction. In central Europe that amounts to only a few degrees. For your planning, the number works perfectly well as a compass – how to derive the light direction from it is shown in the guide Planning the sun position.

Two names for one runway

A runway can be used in both directions, so each end gets its own number. The opposite direction is offset by 180 degrees, which divided by ten is 18. If one number is smaller than 18, you add 18; if it’s larger, you subtract 18. 05 becomes 23, 26 becomes 08, 16 becomes 34. That’s why profiles and charts write runways as a pair, such as 05/23 in Hamburg or 11/29 in Vienna.

Try it yourself: enter a magnetic heading, and the calculator shows you the runway number.

The letters: L, C and R for parallel runways

Many large airports have several runways with the same orientation. So that nobody lands on the wrong one, each gets an additional letter:

• L for left
• C for center
• R for right

What counts is the view from the approach direction, meaning what the pilot sees ahead. That has a consequence that regularly confuses beginners: At the other end, L and R swap. Someone arriving from the west and landing on the left runway toward 08 has the northern runway ahead. Someone arriving from the east and landing toward 26 on the same runway has it on the right. That’s why the north runway in Munich is 08L/26R and the south runway is 08R/26L. A center runway, on the other hand, stays C on both sides.

Airport	Runways	Left runway (smaller number)	Notable feature
Frankfurt	07L/25R, 07C/25C, 07R/25L, plus 18	Northwest landing runway 07L/25R	Runway 18 West is used in one direction only
Munich	08L/26R, 08R/26L	North runway 08L/26R	pure east-west parallel runway system
Berlin Brandenburg	06L/24R, 06R/24L	North runway 06L/24R	since October 3, 2024, previously 07/25
Düsseldorf	05R/23L, 05L/23R	05L/23R	main runway is 05R/23L
Cologne/Bonn	13L/31R, 13R/31L, plus 06/24	long main runway 13L/31R	parallel runways designated 14/32 until April 2024

For spotters, this is more than theory. At the Zeppelinheim viewing platform, landings on 25L pass right by you, while aircraft on 25R touch down far away to the north. So when you hear “runway two five right,” you know right away: this aircraft won’t give you much at this location. At the Munich Airport visitors’ hill (Besucherhügel), too, the letter decides whether an approach passes close by or lands on the other side of the airport.

More than three parallel runways

Three letters won’t get you far with four or five parallel runways. The usual solution: some of the runways get the number that would actually be correct, and the neighboring runways get the next ten-degree number over. The runways are then parallel but carry different numbers.

Well-known examples come from the US, so without a leading zero:

• Los Angeles has four parallel runways with practically the same orientation. They are nevertheless called 6L/24R, 6R/24L, 7L/25R and 7R/25L. Spotters know this from In-N-Out Burger and Imperial Hill, where landings come in from the east.
• Dallas/Fort Worth numbers five parallel north-south runways as 17L, 17C, 17R, 18L and 18R.
• Phoenix, when it built a third parallel runway in 2000, didn’t simply add a C runway but redistributed the existing ones: alongside the new 7R/25L, the two older runways have been called 7L/25R and 8/26 ever since.

In Europe, Amsterdam Schiphol is the best-known example of many runways in a tight space. The north-south runways carry letters there, like the Polderbaan (18R/36L), and then there are runways in completely different directions. From the Spotterplaats at the Polderbaan, it’s worth checking the designators before you set out.

Why runways get renamed

The magnetic north pole wanders, and with it the magnetic variation – the angle between true north and magnetic north. The runway stays where it is, but its magnetic heading slowly shifts. If a runway already sits close to the boundary between two ten-degree steps, a few degrees are enough for it to round to a different number. Then it gets renamed: markings on the asphalt, taxiway signs, approach charts, procedures and databases all have to be updated at the same time. Such changeovers therefore happen on a fixed effective date.

A few examples from recent years:

Airport	Old	New	Effective date
Geneva	05/23	04/22	September 13, 2018
Barcelona	07L/25R, 07R/25L	06L/24R, 06R/24L	March 24, 2022
Lisbon	03/21	02/20	2022
Cologne/Bonn	14L/32R, 14R/32L	13L/31R, 13R/31L	April 18, 2024
Berlin Brandenburg	07L/25R, 07R/25L	06L/24R, 06R/24L	October 3, 2024

At Zurich, the airport decided in 2021 to rename all three runways: 10/28 becomes 09/27, 14/32 becomes 13/31 and 16/34 becomes 15/33. The date has been postponed several times, most recently to 2027. Until then the current designators apply – so at Spectator terrace B you still deal with runways 16/34 and 28.

Where the number doesn’t refer to magnetic north

In regions near the magnetic pole, the compass is unreliable. There, runway numbers are based on true north. This is common in northern Canada, and at Pituffik Space Base in Greenland (Thule Air Base until 2023), the runway carries a T as a suffix: 08T/26T. Such runways don’t have to be renamed when the magnetic variation drifts.

Other suffixes you may come across

Besides L, C and R, there are rare special cases, mostly in North America:

• W marks water runways for seaplanes, for example in Honolulu or at Lake Hood in Anchorage.
• S, G, H and U are used at some small airfields for short takeoff and landing (STOL) aircraft, gliders, helicopters and ultralights.
• Three-digit numbers exist on a few military training runways, which are designated with the full heading.

At German commercial airports, these suffixes play no role. But if you have spots like Maho Beach or US airports on your bucket list, you’ll occasionally read them on charts.

How to use runway designators when spotting

The designator is the link between the weather report, radio, live map and your location. In practice, you proceed like this:

Approach procedures also depend on the designator: An instrument approach is always published for a specific runway and direction. Why that is and what spotters get to see of it is explained in the post on the ILS approach.

Common misconceptions

• “The runway is called 25, so everyone lands toward 25.” No – the number describes only one end. With an easterly wind, the same runway is used as 07.
• “L is always the northern runway.” Only in one direction. At the other end, the same runway is R.
• “The same number means the same runway.” With four or more parallel runways, parallel runways can have different numbers, and after a renaming the same runway carries a new one.
• “The number is the exact heading.” It is rounded and magnetic. That’s enough for light planning; for navigation, pilots use the exact published values.
• “Numbers are different in the US.” Only the spelling: Runway 9 and runway 09 mean the same direction.

Conclusion

Runway designators follow two simple rules: The number is the rounded magnetic heading divided by ten, and the letter is the position from the approaching pilot’s point of view. Everything else follows from that – the 18 as the difference between both ends, the swapping of L and R, the substitute numbers at many parallel runways and the occasional renamings when the magnetic field keeps drifting. Once you’ve internalized that, “RWY 25C” in the weather report turns into a concrete statement about where you should stand today. If you’re just starting out, you’ll find the next steps in the guide Plane spotting for beginners.