Vinyl Record Speed Converter (33 / 45 / 78 RPM)
See the pitch shift, speed change, and running-time change when a vinyl record is played at the wrong RPM (33⅓, 45, or 78). Runs in your browser.
Playing a record at the wrong speed multiplies playback rate by (played RPM ÷ recorded RPM), which shifts pitch by 12·log₂(ratio) semitones and changes the running time inversely. A 33⅓ disc spun at 45 plays ~35% faster and about 5.2 semitones higher (the “chipmunk” effect); a 45 at 33⅓ plays slower and lower. Pitch and tempo shift together — unlike digital time-stretching, which can change one independently. Everything runs in your browser.
About this tool
Vinyl records are cut to play at one of three standard rotational speeds — 33⅓ RPM (the long-playing album), 45 RPM (the single), and the older 78 RPM (shellac records) — and playing one at the wrong speed audibly changes both its pitch and its tempo together. This converter quantifies that effect. When you play a disc recorded for one speed at another, the playback rate is multiplied by the ratio of the two speeds (played RPM ÷ recorded RPM). Because pitch is logarithmic, that speed ratio translates to a pitch shift of 12 · log₂(ratio) semitones, and the running time changes inversely (faster playback means a shorter, higher-pitched result; slower means longer and lower). For example, the classic mistake of spinning a 33⅓ album at 45 makes it run about 35% faster and roughly 5.2 semitones higher — the familiar 'chipmunk' sound — while a 45 single played at 33⅓ drags slower and drops in pitch. The tool reports the pitch shift in both semitones and cents, the percentage speed change, and the new track length given the correct-speed duration. A key conceptual point it highlights: with analog speed change, pitch and tempo are inseparably linked because both come from the same rotation rate — this is unlike digital time-stretching or pitch-shifting, which can alter one while holding the other constant. DJs exploit small speed adjustments (the turntable pitch fader) to beat-match, and producers sometimes record or replay at half/double speed deliberately for effect. The math here also explains why a slightly-off turntable speed throws a whole record subtly out of tune. Everything runs in your browser; nothing is uploaded.
How to use it
- Select the speed the record was recorded for (33⅓, 45, or 78 RPM).
- Select the speed you are playing it at.
- Enter the track's correct-speed length.
- Read the pitch shift (semitones/cents), the speed change percentage, and the new playback length.
Frequently asked questions
- What happens if I play a 33 RPM record at 45?
- It plays about 35% faster and roughly 5.2 semitones higher in pitch — the "chipmunk" effect. Both speed and pitch rise together because they come from the same rotation rate.
- How is the pitch shift calculated?
- Playback ratio = played RPM ÷ recorded RPM. Pitch shift in semitones = 12 · log₂(ratio). A ratio of 1.35 (33⅓→45) is about +5.2 semitones; the inverse (45→33⅓) is about −5.2.
- Does the song get shorter or longer?
- Running time changes inversely to speed. Faster playback (higher RPM than intended) shortens the track; slower playback lengthens it. The tool shows the new duration from the correct-speed length.
- Why do pitch and tempo change together on vinyl?
- Both are governed by the rotation speed, so changing RPM scales them by the same factor. Digital tools can decouple them (time-stretch or pitch-shift independently); a turntable cannot.
- Why does a slightly wrong turntable speed sound off?
- Even a 1–2% speed error shifts the whole record by a fraction of a semitone, enough to sound subtly sharp or flat — especially noticeable alongside other instruments or a reference pitch.
- Is anything uploaded?
- No. All calculations run entirely in your browser.