Runway Number Calculator
A runway number equals its magnetic heading divided by 10 and rounded to the nearest whole number.
09 × 10 = 90° magneticSuffix L marks position, not heading
Every Runway Number and Its Reciprocal
All 36 designators are listed below with their magnetic headings and opposite ends, so every runway pair differs by exactly 18 and every heading pair by exactly 180°.
| Runway | Heading | Opposite | Its heading |
|---|---|---|---|
| 01 | 010° | 19 | 190° |
| 02 | 020° | 20 | 200° |
| 03 | 030° | 21 | 210° |
| 04 | 040° | 22 | 220° |
| 05 | 050° | 23 | 230° |
| 06 | 060° | 24 | 240° |
| 07 | 070° | 25 | 250° |
| 08 | 080° | 26 | 260° |
| 09 | 090° | 27 | 270° |
| 10 | 100° | 28 | 280° |
| 11 | 110° | 29 | 290° |
| 12 | 120° | 30 | 300° |
| 13 | 130° | 31 | 310° |
| 14 | 140° | 32 | 320° |
| 15 | 150° | 33 | 330° |
| 16 | 160° | 34 | 340° |
| 17 | 170° | 35 | 350° |
| 18 | 180° | 36 | 360° |
| Runway | Heading | Opposite | Its heading |
|---|---|---|---|
| 19 | 190° | 01 | 010° |
| 20 | 200° | 02 | 020° |
| 21 | 210° | 03 | 030° |
| 22 | 220° | 04 | 040° |
| 23 | 230° | 05 | 050° |
| 24 | 240° | 06 | 060° |
| 25 | 250° | 07 | 070° |
| 26 | 260° | 08 | 080° |
| 27 | 270° | 09 | 090° |
| 28 | 280° | 10 | 100° |
| 29 | 290° | 11 | 110° |
| 30 | 300° | 12 | 120° |
| 31 | 310° | 13 | 130° |
| 32 | 320° | 14 | 140° |
| 33 | 330° | 15 | 150° |
| 34 | 340° | 16 | 160° |
| 35 | 350° | 17 | 170° |
| 36 | 360° | 18 | 180° |
Runway 36 rather than 00 marks north, because the numbering runs 01 through 36 with no zero. Once the headings are in hand, feed them into the multi-runway wind comparison to see which end suits the day's wind.
The rounding hidden in this table is worth understanding, because it is the single largest source of error when comparing a runway against a reported wind. A designator covers a ten-degree band: runway 09 is anything from 085° through 094°, so two runways both labelled 09 at different airports can differ by nine degrees of actual heading. On a 20-knot wind at a shallow angle, that rounding is worth roughly three knots of crosswind, small, but the same order as the difference that decides between two runways. Airport charts publish the surveyed heading to a tenth of a degree precisely so the exact figure is available when it matters.
What L, C, and R Mean on Parallel Runways
A letter suffix identifies which of several parallel runways you are cleared to, and carries no information about heading, all parallels on a given number share the same magnetic direction.
Left
Suffix LThe leftmost runway of a parallel set, as seen by an aircraft approaching on that heading. At Los Angeles, 25L is the southern of the two northern-complex runways when landing westbound.
Centre
Suffix CThe middle runway where three parallels share a heading. Only a handful of airports need it, Atlanta, Dallas/Fort Worth and Amsterdam among them, and it disappears if a parallel closes.
Right
Suffix RThe rightmost of the set on that heading. Because the suffix is relative to the direction of travel, the runway called 25R landing west is 07L landing east: the same concrete, the opposite side.
Where four or more parallels exist, the convention breaks down and airports offset the numbers instead. Los Angeles labels its four as 06L/06R and 07L/07R even though all four point within a degree or two of the same direction, because there is no fourth letter available. Atlanta does the same with 08L/08R and 09L/09R across five parallel strips.
Why Airports Renumber Runways
Airports renumber runways because magnetic north moves and runway designators are tied to the magnetic compass, so a heading that rounded to 270° when the runway was painted can round to 280° a few decades later.
The magnetic north pole drifts continuously, and the rate is not uniform across the globe. In much of the continental United States variation changes by roughly a tenth of a degree per year; in parts of Alaska it moves considerably faster. A runway sitting near a rounding boundary , say a true heading that gives 274.6° magnetic, needs only a small drift before 275° tips it into the next designator.
The consequences are administrative rather than physical. Oakland's runway 27 became 28, and Fort Lauderdale, Tampa, and a number of Alaskan fields have all shifted within living memory. Each change means repainting the numbers and the holding-point signage, reissuing the airport diagram, amending every instrument approach chart that references the runway, and updating the navigation database in every avionics unit that carries it. Airports therefore batch renumbering with resurfacing or other major works wherever they can. The underlying arithmetic never changes, which is why the same conversion appears in the wind formula reference sheet and why comparing a runway against a reported wind on the crosswind component lookup works identically before and after a renumbering.
Runway Numbering Questions
Why did some airports change their runway numbers?
Magnetic north drifts, and runway numbers are magnetic. When the magnetic heading of a runway moves far enough that it rounds to a different multiple of ten, the designator has to change or charts and instrument procedures stop matching the compass. Oakland renumbered 27 to 28, and several Florida and Alaskan fields have shifted in recent decades. The pavement never moves; the reference does.
What does the L, C, or R after a runway number mean?
The letter marks position within a set of parallel runways, not a different heading. Two parallels are L and R, three are L, C and R, and all of them share the same magnetic direction. Because the label describes what a pilot sees on approach, the same strip of concrete carries opposite letters at its two ends: 09L one way is 27R the other.
Is runway heading true or magnetic?
Runway numbers are magnetic almost everywhere in the world, which is what lets you compare them directly against the magnetic compass and against tower-reported wind. The exception is the far north, where some Canadian airports inside the Northern Domestic Airspace use true headings because magnetic variation near the pole is too large and unstable to be useful. Airport charts publish the precise true bearing separately, usually to a tenth of a degree.
Can two different airports have the same runway number?
Yes, and most do. There are only 36 possible numbers, so runway 09 exists at thousands of airports worldwide. The designator identifies a direction at a specific field, never a unique location. This is why clearances always pair a runway with an airport, and why entering the wrong airport into a GPS produces an approach that lines up convincingly with entirely the wrong piece of ground.
How often does magnetic variation cause a renumbering?
Rarely for any single runway, typically once every few decades, and never for some. Magnetic variation drifts by roughly a tenth of a degree per year in most of the world, so it takes many years to accumulate the five degrees needed to cross a rounding boundary. Airports usually batch the change with other work, because renumbering means repainting the threshold, reissuing charts, and amending every instrument procedure that references it.