Airplane Seat Recline Measurement... in units of length inches?

Perhaps this is conspiracy, but what is the meaning of seat recline measurement in unit of length inches? How is it measured? Does industry standard exist? What is the interpretation in relation to reported recline angle? I try using google search engine but only results related to ethics of reclining a seat or definition of seat pitch.

To be clear, this question is not about seat pitch, seat width, or the person sitting behind me.

I understand that airline marketing team try to obscure this because of ethics or consumer realizing that reported recline actually poor in reality, so please make comment on comparability between airlines with seat recline length or angle (in context of measurement methodology; e.g., if both Airline A and B report 8" recline then is recline equal in reality, or if both report 120° degrees is recline equal in reality)?

For example, Singapore Airline SQ reporting premium economy recline as 8" (I assume double quote meaning inch). Cathay Pacific CX also reporting 8 inch recline. US-based airliner not even attempting to advertise seat recline.

I have heard this recline length is related to maximum horizontal movement of seat during recline action, so I suppose seat height cheating could affect the interpretation.

A picture would be great!

Here is a website compiling seat recline; some have recline in units of length, while others are angle in degrees. I assume that 90 degrees is vertical, but I cannot trust the airline marketing team.

• It is simply a marketing pitch without industry wide standards.
– user13044
Feb 21, 2017 at 9:06
• draw two planar objects fomring an L shape, with the size of the airplane seat. Add the inches to the top left corner of the L. make a line between the furthest point of the (now weird) L on the left to the central vertex of the L. that's how much you'll be able to recline "at most". if it's n" of displacement, it could be measured at the core material of the seat ( without padding). Mar 2, 2017 at 11:05

The recline in inches is the distance the head-rest moves towards the back of the plane. In mathematical terms, it's the height of the seat-back in inches times the difference between the cosine of the original seat angle and the cosine of the final seat angle.

For example if seat is 30" high and declines from 100° to 118°, that is

``````30 * (cos(100°) - cos(118°)) =
30 * (-0.1736482 - -0.469472) =
8.8747"
``````
• It'd be nice to add a visual aid as well. Mar 15, 2017 at 18:57
• @JonathanReez -- if you'll draw it, I'll add it to the answer. Mar 16, 2017 at 17:39