How seat width is measured, and why numbers disagree
Look up the same seat on three websites and you may get three different widths. None of them are necessarily lying. They're measuring different things.
The two measurements
- Between the armrests: the gap you actually sit in. This is the honest number for "will I fit," and it's the one airlines like KLM, Alaska, Air France, and Allegiant publish when they publish anything.
- Cushion width: the upholstered pad, which can run under the armrests. Marketing pages and some third-party seat maps prefer it, because it's an inch or two bigger.
That inch or two is exactly the gap you'll see between sources. When a third-party seat map says 18 inches and the airline itself says 16–17.7 armrest-to-armrest (this is literally the case at Air France), the likeliest explanation isn't a conspiracy. It's two tape measures on two different things.
Why we lead with the smaller number
Every range and every disagreement on this site is presented smallest-number-first, and we call that the planning number. The reasoning is simple: if you plan for 16 inches and find 18, your flight just got better. If you plan for 18 and find 16, you have a problem at 35,000 feet. For our readers, the optimistic error is the harmful one, so we don't make it.
Why we sometimes show two numbers that disagree
When sources conflict and the airline won't settle it (often because the airline publishes nothing at all), we show both figures and say where each came from, rather than quietly picking one. A site that silently "resolves" conflicts is guessing on your behalf. We'd rather hand you the disagreement honestly, with the safer number first.
Three habits for reading any seat-width figure, anywhere
- Check whose number it is. Airline's own page beats a third-party seat map; a dated source beats an undated one. (Every figure on SeatRuler is labeled this way.)
- Assume armrest-to-armrest unless told otherwise, and if a number looks generous, suspect it's cushion width.
- Mind the aircraft, not just the airline. The same airline can fly the same route with an 18.6-inch A220 seat one day and a 17.3-inch 737 seat the next.