# Why don't runway numbers exceed the number 36?

Hey guys!
For a while, before I knew much about aviation, I always wondered why runway numbers at every airport worldwide didn’t exceed the number, 36. I thought I’d write this topic just to explain it to those who maybe didn’t know why, or didn’t even notice!

So, when looking the pictures below, which I’ve taken from numerous airports worldwide, we see none of the runway numbers pass the physical number 36.

KJFK, all runways.
Source

London Heathrow.
Source

Sydney International.
Source

Miami Intl’.
Source

Now, you may be asking yourself why don’t the runways exceed the number 36?

The answer, simple. The numbering of runways are based on their magnetic bearing, or what heading the aircraft is at, at runway heading!

The more complex answer, can be found below :)

Consider a plane flying toward the runway on final approach in a day without any wind. Divide its magnetic heading by 10, round it to the nearest whole number and you’ll usually get the runway number. For example, if the magnetic heading is 345° then 345/10=34,5, so the runway number will be 35 which will be a runway used for landings (and takeoffs) to the north.

Opposite ends of the same runway have different numbers, 18 (which represents 180 degrees) apart. A runway with 35 for landings to the north will have runway 17 for landings to the south. Even though these are the same strip of concrete, they are treated as separate runways by pilots and controllers.

If there are two airports near one another with runways at the same angle, sometimes one of the airports will add or subtract one from the runway number to help planes differentiate between the airports.

Occasionally a runway number will change when the magnetic declination angle changes in such amount, making the runway magnetic bearing divided by 10 and rounded to the nearest whole number increase or decrease.

Some runways in areas of large magnetic declination use true instead of magnetic headings for the runway numbers. This is not unusual in northern Canada and Greenland.

When there is more than one parallel runway at an airport, L, R, or C may be appended to the runway number for Left, Right, or Center. These are based on the approach direction, so, for example, the runway 35L would be called 17R from the opposite direction.

Cool! But I don’t need to know.

This is a duplicate
Very likely, I’m sorry in advance.

I hope you guys enjoyed this little piece of (i hope) cool information about runway numbering, and maybe even learned a thing or two!
Kev :)

19 Likes

Correction: Why don’t runway numbers exceed 36?

For example:

6 Likes

I didn’t, sorry, because it was factually wrong D:

But nice post, anyway.

Incorrect.
Look at EHAM. 3 Runways with the heading of 360. (36/18LCR)
Nice post though

1 Like

Runways are based off of 360s. So 35 would be 350 degrees and so forth. And the opposite of 35 would be RW 17 or 170s and so forth

4 Likes

Thanks for the correction @emil @N1DG @DeerCrusher. Fixed.

2 Likes

Because there are only 360 degrees in a circle…

7 Likes

Cool! Thanks for the input!

1 Like

Runways are based off of what heading they are pointing, so if a runway is aiming at the heading of 260 degrees then the runway number is runway 26, since 360 is the maximum heading, the runway numbers stop at 36, just wanted to point it out even though the others already stated it :) .

2 Likes

Excellent post Kevin! I love to see more useful and informative #real-world-aviation posts lately ❤

1 Like

The runway number gives the flight crew a rough idea of the runways QDM (magnetic bearing) hence an idea of the inbound course to the associated runway.

Useful if you’re diverting and don’t have the plates or approach charts for an airfield.

5 Likes

The runway numbers are indicated by its heading eg runway 25 is approached at a heading of around 250. 36 is the last number because 360 heading is the runway heading.
In Aviation, the heading is similar to a circle which has a maximum of 360 degrees. Hope this helps.
CHEERS :)

1 Like

I don’t mean to be rude, and I see how much effort you have put into this post. I think we all have wondered why sometime, but in an avgeek forum… I honestly think that pretty much everyone, if not everyone, knows this.

2 Likes

It is useful especially when determining the best runway to land on during gusts

1 Like

Thanks George! Even though I just noticed this was quite an easy answer 😂!

1 Like

@Kevin MaxSez: lotta time and effort there Kevin, well done. Appears you may have initially missed the earth science/basic math class along the way. Most of us got it early on. Next time consider addressing how to compute “Reciprocals”. An extremely important math problem in flight planning and pattern work.

4 Likes

Thanks Max, suffered from a good old “brain fart”. Will make sure to add that at some point!

2 Likes

What ?

1 Like

Photoshop… there isn’t a runway that exceeds the number 36.

1 Like

I’d just use the first two digits of the heading :)

1 Like