Vinyl RPM Calculator — Play Time, Groove Spacing & Velocity

Calculate groove spacing, linear velocity, and play time for vinyl records at any RPM, diameter, and groove density

Estimated Play Time

17:09 per side

Total Grooves

572

Groove Length

1,151 ft

Record Size

Outer Diameter (in)

Inner Diameter (in)

Custom RPM

Lines Per Inch (LPI)

LPI (Lines Per Inch): How tightly the grooves are packed. Higher LPI = more play time but reduced audio quality. Standard LPs average 100–200 LPI.

Estimated Play Time (per side)

17:09

minutes

Grooves

572

Length

1,151 ft

Spacing

6.7 mil

Linear Velocity

Outer Edge20.07 in/s

Inner Edge6.76 in/s

Average13.42 in/s

Higher velocity = better audio quality. Inner grooves have lower velocity, which is why audio quality decreases toward the end of a side.

Record Geometry

Playable Width3.813"

Outer Circumference36.13"

Inner Circumference12.17"

Total Groove Length1,151 ft (0.22 mi)

Standard Formats

Format	RPM	Typical Time/Side
7" Single	45	4–6 min
10" EP	33 1/3	12–15 min
12" LP	33 1/3	18–22 min
12" Single (audiophile)	45	12–15 min

Example Calculations

1Standard 12" LP at 33 1/3 RPM

Inputs

Record Diameter12"

Inner Diameter3.875"

RPM33.33

Groove Density150 LPI

Result

Estimated Play Time17:10 per side

Total Grooves572

Groove Length1,411 ft

Groove Spacing6.7 mil

Effective outer radius = 6 - 0.25 = 5.75". Inner radius = 1.9375". Playable width = 3.8125". Total grooves = 3.8125 × 150 ≈ 572. Play time = 572 / 33.33 ≈ 17.2 min. Groove length = π × 150 × (5.75² - 1.9375²) ≈ 13,818 in ≈ 1,152 ft.

27" Single at 45 RPM

Inputs

Record Diameter7"

Inner Diameter3.875"

RPM45

Groove Density150 LPI

Result

Estimated Play Time4:23 per side

Total Grooves197

Groove Length354 ft

Groove Spacing6.7 mil

Effective outer radius = 3.5 - 0.25 = 3.25". Inner radius = 1.9375". Playable width = 1.3125". Grooves = 1.3125 × 150 ≈ 197. Play time = 197/45 ≈ 4.4 min.

3Audiophile 12" at 45 RPM

Inputs

Record Diameter12"

Inner Diameter3.875"

RPM45

Groove Density100 LPI

Result

Estimated Play Time8:28 per side

Total Grooves381

Groove Length940 ft

Groove Spacing10.0 mil

Playable width = 5.75 - 1.9375 = 3.8125". Grooves = 3.8125 × 100 ≈ 381. Play time = 381/45 ≈ 8.47 min. Wider grooves at 45 RPM provide superior audio quality.

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Frequently Asked Questions

How long can a vinyl record play per side?

Play time depends on record diameter, RPM, and groove density (LPI). A standard 12" LP at 33 1/3 RPM with average groove density plays about 18–22 minutes per side. Increasing groove density extends time but reduces audio quality. A 7" single at 45 RPM holds about 4–6 minutes per side.

12" LP at 33 1/3 RPM: 18–22 minutes per side (standard)
12" LP at 33 1/3 RPM: up to 30 min per side (high density, reduced quality)
12" single at 45 RPM: 12–15 minutes per side (audiophile quality)
10" EP at 33 1/3 RPM: 12–15 minutes per side
7" single at 45 RPM: 4–6 minutes per side

Format	RPM	Typical Play Time	Quality
12" LP	33 1/3	18–22 min/side	Standard
12" Single	45	12–15 min/side	Audiophile
10" EP	33 1/3	12–15 min/side	Standard
7" Single	45	4–6 min/side	Standard
7" EP	33 1/3	7–9 min/side	Reduced

What is groove spacing (LPI) and how does it affect sound quality?

LPI (Lines Per Inch) measures how tightly grooves are packed on a record. Standard LPs use 100–200 LPI. Higher LPI means more play time but narrower grooves, which reduces dynamic range and increases distortion. Audiophile pressings use lower LPI (80–120) for wider grooves and better fidelity.

80–120 LPI: Audiophile quality, wider grooves, louder cut
120–180 LPI: Standard commercial pressing
180–250 LPI: Extended play, reduced dynamics
250–300 LPI: Maximum play time, noticeable quality loss
Groove width varies with signal amplitude (louder = wider modulation)

LPI Range	Quality	Typical Use	Play Time Impact
80–120	Excellent	Audiophile 45 RPM	Shorter
120–180	Good	Standard LP	Normal
180–250	Acceptable	Budget pressings	Longer
250–300	Poor	Spoken word, compilations	Maximum

Why does audio quality degrade toward the inner grooves?

Inner grooves have a smaller circumference, so the stylus moves slower relative to the groove modulation (lower linear velocity). At 33 1/3 RPM on a 12" LP, outer velocity is about 20.5 in/s while inner velocity drops to about 8.5 in/s. This 60% reduction causes inner groove distortion, less high-frequency detail, and more tracking difficulty.

Outer edge linear velocity: ~20.5 in/s (12" LP at 33 1/3)
Inner edge linear velocity: ~8.5 in/s (same LP)
CD equivalent: constant 1.3 m/s from start to finish
45 RPM increases inner velocity by 35%, reducing distortion
Mastering engineers sequence quieter/simpler tracks near the center

Speed	Outer Velocity	Inner Velocity	Velocity Ratio
33 1/3 RPM	20.5 in/s	8.5 in/s	2.4:1
45 RPM	27.7 in/s	11.5 in/s	2.4:1
78 RPM	48.1 in/s	19.9 in/s	2.4:1

What are the standard vinyl record speeds and when is each used?

33 1/3 RPM is the standard for 12" LPs and 10" EPs since 1948. 45 RPM is used for 7" singles and audiophile 12" pressings. 78 RPM was the pre-LP standard (shellac discs). 16 2/3 RPM was briefly used for spoken word but is now obsolete.

16 2/3 RPM: Obsolete, used for spoken word records in the 1950s
33 1/3 RPM: Standard LP speed since 1948 (Columbia Records)
45 RPM: Standard single speed since 1949 (RCA Victor)
78 RPM: Pre-LP shellac records (1898–1950s)
Variable speed turntables can play at ±8% for pitch adjustment

How long is the groove on a vinyl record?

A standard 12" LP at 150 LPI has a continuous spiral groove about 1,500 feet (0.28 miles) long per side. A 7" single has roughly 300–400 feet. The groove starts at the outer edge and spirals inward. The total length depends on groove density and playable area.

12" LP at 150 LPI: ~1,500 ft (0.28 miles) per side
12" LP at 100 LPI: ~1,000 ft (0.19 miles) per side
7" single at 150 LPI: ~350 ft per side
The groove is one continuous spiral, not concentric circles
Groove width is about 0.001–0.003 inches (1–3 mils)

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Vinyl RPM Calculator — Play Time, Groove Spacing & Velocity

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