Vinyl Record Size and Speed Chart
Vinyl comes in three common diameters and three playback speeds, and the pairings are conventions rather than rules, which is exactly why records sometimes get played at the wrong speed. This chart lists each format with its usual speed, typical runtime per side, and the cases where the convention does not hold.
The three record sizes
12 inch (30cm): the LP format, usually played at 33 1/3 RPM with roughly 20-25 minutes per side. Also used for 45 RPM singles and EPs, where the faster speed and wider groove spacing improve sound quality at the cost of runtime.
10 inch (25cm): an older format, common for 78 RPM shellac records historically and used today for special editions and some EPs, typically at 33 1/3 or 45 RPM with around 12-15 minutes per side.
7 inch (17cm): the classic single, almost always played at 45 RPM with roughly 4-6 minutes per side, which is why 45 became shorthand for a single in the first place.
The three playback speeds
33 1/3 RPM: the standard LP speed, prioritizing runtime over fidelity, which is how a full album fits on one disc.
45 RPM: faster groove speed carries more information per second, giving better dynamics and high-frequency detail, which is why audiophile reissues are often cut at 45 RPM across two discs instead of one 33 RPM disc.
78 RPM: the pre-1950s shellac standard, largely obsolete but still collected. These need both a turntable that supports 78 RPM and, critically, a different stylus.
78s need a different stylus, not just a different speed
Modern microgroove records (33 and 45 RPM) use a groove that fits a stylus tip around 0.7 mil, while 78 RPM shellac records have much wider grooves needing roughly a 3 mil stylus. Playing a 78 with a modern stylus means the tip rides the bottom of the groove instead of its walls, producing poor sound and potentially damaging the record.
This is why turntables advertising 78 RPM support are only half the solution: without a dedicated 78 stylus or a swappable cartridge, the speed setting alone will not play shellac properly.
When the convention does not hold
Plenty of records break the usual pairings: 12 inch singles at 45 RPM were a club staple for decades, some 7 inch records are cut at 33 RPM to fit longer material, and modern audiophile pressings frequently split an album across two 45 RPM discs. Always check the label or sleeve rather than assuming the speed from the diameter.
If a record sounds too slow and muddy or too fast and chipmunk-like, the speed setting is almost always the cause, and it is a harmless mistake to correct: switching speeds mid-play does not damage anything, unlike using the wrong stylus.