Vinyl record runtime calculator
A record side trades length against level: louder cuts need wider grooves, and wider grooves mean less time.
grooves per mm
Playing time per side
0:20:38
- In minutes
- 20.64
- Revolutions
- 688
- Total groove length
- 445.3
- Groove speed at the outer edge
- 0.5096 m/s
- Groove speed at the inner edge
- 0.2094 m/s
- Inner to outer speed ratio
- 0.4110
Show the working
- Record size = 12
- Speed = 33.3333
- Groove pitch = 8
- Outer recorded radius = 146
- Inner recorded radius = 60
- band_width = max(146 - 60, 0) = 86
- Revolutions = 86 * 8 = 688
- In minutes = 33.3333 > 0 ? 688 / 33.3333 : 0 = 20.64
- Playing time per side = 20.64 * 60 = 1238.4
- Total groove length = 688 * 2 * pi * (146 + 60)/2 / 1000 = 445.252
- Groove speed at the outer edge = 2 * pi * 146/1000 * 33.3333 / 60 = 0.509 636
- Groove speed at the inner edge = 2 * pi * 60/1000 * 33.3333 / 60 = 0.209 44
- Inner to outer speed ratio = 0.509 636 > 0 ? 0.209 44/0.509 636 : 0 = 0.410 959
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- revolutions = recorded band width x grooves per mm
- time = revolutions / speed in rpm
The inner grooves move much slower past the stylus, which is why high frequencies and sibilance distort most at the end of a side.
Cutting quieter allows a finer pitch and a longer side. Loud 12-inch singles are short for exactly this reason.