Up to eleven

C&O's No. 500 first went "up to 11" in 1947.

The use of "11" as a maximum pre-dates This Is Spinal Tap by almost forty years. In 1947, the Baldwin Locomotive Works and the Chesapeake and Ohio Railway introduced the Chesapeake and Ohio class M-1 steam turbine locomotive. The locomotive's throttle included eleven settings, ranging from one (idling) to eleven (full speed). The locomotive's cruising speed was 70 miles per hour (113 km/h), at which point the throttle was on "seven". During a trial run with a reporter from Popular Mechanics aboard, a C&O engineer expressed his dissatisfaction with a local speed limit of 75 miles per hour (121 km/h), noting that he would "Sure like to be able to pull it back to eleven!"[4]^{:110; 252}

In quality equipment multipole switches are sometimes used for volume controls, usually with 23 detents, wired with a resistor chain. These give 23 positions with the first being silent, so were numbered 0-11 (0-22 is impractical). Potentiometers give a much more finely adjustable volume, but the same numbering was used. This is how Marshall amplifiers came to have controls numbered 0-11.

Gibson Les Paul guitars with low-impedance pickups were outfitted with special controls designed by Les Paul himself. Controls included a "Decade Switch" that went up to 11.[5]

All teams in racing have various modes and settings that they switch to depending on the necessary strategy of the race. From time to time teams will use special phrases or keywords to describe the modes. The Red Bull Racing team in Formula 1 refers its drivers over the radio to "Mode 11", which is an engine mode that unlocks the full power of the engine, encouraging the driver to challenge the cars ahead.

As a consequence of the film, real bands and musicians started buying equipment whose knobs went up to 11, or even higher, with Eddie Van Halen reputedly being the first to do so.[6] Marshall, the company that provided amplifiers for the film that the custom-marked knobs were applied to, now sells amplifiers such as its JCM900 (first sold in 1990) whose knobs are marked from 0 to 20.[6][7] The QSC 3500 and 3800 amplifiers made for the professional sound company Sound Image in the 1990s went to 11, as do amps from Soldano and Friedman.

Other controls with a maximum of 11 include SSL mixing consoles, Amazon Alexa, the BBC's iPlayer on demand video player,[8] the headphone volume control on the PreSonus AudioBox 1818VSL, the volume control on the Apogee Mini-DAC,[9] the IRIX audio panel (when invoked with the undocumented -spinaltap option), and the Tesla Model S's volume control.[10] The tachometer on a Singer Vehicle Design modified Porsche 911 goes up to 11, representing 11,000 RPM.[11][12]

On its primary page for This Is Spinal Tap, the IMDb displays the user rating for the film out of 11 stars (e.g. 7.9/11) instead of the standard scale of one to ten.[13][14][15] However, only 10 rating stars are actually shown on the page, and user ratings can only be submitted up to 10 stars. Other IMDb pages display the rating out of 10.[14]

The influence of the phrase "up to eleven" is such that it has been used outside of music; in 2016, for example, astronomer Krzysztof Stanek described the brightest-known object in the universe as being "as if nature took everything we know about magnetars and turned it up to 11."[16]