Comparison

Engine RPM vs Spin Counter Plus

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Engine RPM

Analyze engine sound to calculate RPM using advanced signal processing. Ideal for engine setup and diagnostics, it supports various engine types and provides real-time feedback for accurate readings.

Highlights
  • Acoustic RPM measurement
  • Engine sound analysis
  • Supports 2-stroke/4-stroke engines
  • Configurable cylinder count
  • Real-time autocorrelation graph
  • Adjustable update periods
  • Low-pass filtering
Features
Read full description

Measure the RPM of an engine by analyzing the sound it makes. Engine RPM listens to the sound of a running engine and uses advanced signal processing algorithms to extract the frequency of that sound and calculate the RPM. This app is primarily for setup and diagnostics of engines. After setting the the number of cylinders and whether the engine is a 2-stroke or 4-stroke engine, the app can work with any internal combustion engine, from diesel tractors to aircraft engines to motorcycles to chainsaws. To use the app you must set an expected RPM range to guide the analysis algorithms to the correct RPM. A real-time graph of the autocorrelation graph is displayed to help in troubleshooting and adjusting the expected RPM range. The analysis requires a clear sound from the engine without excessive interference from extraneous sounds. Do not expect to read the RPM of an engine while other things are making too much noise at the same time. The analysis also requires that the RPM be stable. It cannot read the RPM of an engine that is rapidly accelerating. For this reason, and because of the need for adjusting the expected RPM range, this app should not be considered a drop-in replacement for an operational tachometer. Setup options include update periods from 93 milliseconds to 1.5 seconds, one to 12 cylinders, 2-stroke or 4-stroke, low-pass filtering, and signal clipping. The overall RPM range is 400 to 90,000 RPM (although at any one time, the operational range is typically +/- 30% around a nominal expected RPM). Precision is usually about +/- 10 RPM.

About

Spin Counter Plus

This utility tool accurately counts rotations using your device's magnetic sensor. It provides detailed data on orientation, speed, and total spins, with options to save or copy the information for further analysis. Ideal for tracking circular motion in sports or activities.

Highlights
  • 3D compass for orientation
  • Tap to start/stop recording
  • Save rotation data images
  • Copy data to clipboard
  • Display total rotations
  • Show rotation speed (sec/RPM)
Features
Read full description

Spin Counter is a utility tool to find the rotation count fast and easy. This app uses magnetic sensor to get compass orientation data and calculate spin count. Features: • 3D compass shows current orientation. • Toggle Tap to start or stop record compass orientation data. • Save Rotation Data Image into camera roll. • Copy Rotation Data to Clipboard for advance operation. • Show Total rotations in seconds. • Show average, fastest and slowest rotation speed in second and RPM. Sample Rotation Data: [253.035686492919922, 250.90165710449219, ... , 180.697193145751953] These are the raw data from device magnetic sensor with each value 0.01 sec interval, meaning that it took 0.01 seconds from angle 253.035686492919922 to 250.90165710449219. Example Usage: - Count Ballet Dancer Spin with the device in a pocket. - Count Skating spins with the device in a pocket. - Count fun fair spinning ride speed. - Any sport activity involving circular motion, such as car drifting etc. - And anything base on your imagination. Thanks for your support and do visit nitrio.com for more apps for your iOS devices.

Screenshots

Engine RPM3 screens
Spin Counter Plus4 screens

Verdict

The call

The clearest difference is price: Spin Counter Plus at $2.99 against Engine RPM's $8.99. Engine RPM's advantage is update cadence (every 16 months vs every 38 months). On ads, in-app purchases, device support and iOS requirement there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Engine RPM costs $8.99 and Spin Counter Plus $2.99 up front. Neither carries in-app purchases, so what you see is what you pay.

UpkeepUpdate frequency

Engine RPM ships an update every 16 months, Spin Counter Plus every 38 months. The most recent releases landed on November 6, 2026 and November 3, 2026 respectively.

Scorecard3 real differences · 7 level
Engine RPM versus Spin Counter Plus: the parameters behind the verdict, then further details
ParameterEngine RPMSpin Counter Plus
Price$8.99$2.99 — better
Rating4.0 (35 ratings) — better—
Positive reviews47.7% of reviews—
Number of ratings35 — better—
Update frequencyEvery 16 months — betterEvery 38 months
AdsNoNo
In-app purchasesNoNo
MonetizationFree — betterPaid
DevicesiPhone, iPodiPhone, iPad, iPod — better
Requires iOS13.012.0 — better
Further details — not scored
Size3 MB10 MB
Age rating4+4+
DeveloperReal-Time SpecialtiesHeng Jia Liang

Customer experience

Engine RPM

All ratings35 ratings
Positive74.3%
Neutral2.9%
Negative22.9%
Written reviews65 reviews
Positive47.7%
Neutral7.7%
Negative44.6%

Spin Counter Plus

All ratings1 ratings
Positive0.0%
Neutral0.0%
Negative100.0%

Bugs and requests

Engine RPM

Reported bugs

12 issues
  • Does not register live RPM readings
  • Displays incorrect or random numbers
  • App opens then closes immediately
  • Blank display or flashes incorrect data intermittently
  • Cannot get consistent readings
Show 7 more
  • Does not work on specific devices (e.g., iPhone 6)
  • E-motor measurement not possible
  • Readings are not accurate
  • Cannot get a reliable reading
  • Randomly skips between significantly different numbers
  • Generates random numbers
  • Does not recognize sound correctly

Requested features

5 requests
  • Save configuration settings
  • Option to display cycle/cylinder count on home screen
  • Improved response time for transient surges
  • Simplified or automated setup process
  • Auto-scaling graphical display for easier harmonic matching

Spin Counter Plus

Not enough reviews yet to summarise bugs or requests.

In-app purchases

None

Engine RPM

No in-app purchases

None

Spin Counter Plus

No in-app purchases

Questions

Is Engine RPM free?
Engine RPM costs $8.99, with no in-app purchases.
Is Spin Counter Plus free?
Spin Counter Plus costs $2.99, with no in-app purchases.
Do Engine RPM or Spin Counter Plus have ads?
Neither Engine RPM nor Spin Counter Plus shows ads.
Which is updated more often, Engine RPM or Spin Counter Plus?
Engine RPM ships an update every 16 months, and Spin Counter Plus every 38 months. Most recently, Engine RPM was updated on November 6, 2026 and Spin Counter Plus on November 3, 2026.

Other comparisons