Copyright & Privacy
RPMCalc — Engine RPM From Sound
C&S Industries, LLC ("we," "us," or "our") develops and publishes RPMCalc. This page covers both our copyright notice and our privacy disclosure. In short: RPMCalc does not collect, store, or share any personal data — the only sensor it uses is the microphone, and that audio never leaves your device.
Copyright
© 2026 C&S Industries, LLC. All rights reserved.
RPMCalc — including its name, icon, user interface design, and source code — is the property of C&S Industries, LLC. Unauthorized reproduction or distribution of this application, or any portion of it, is strictly prohibited.
Microphone Use
RPMCalc uses your iPhone's microphone (via Apple's AVFoundation framework) to listen to engine sound and estimate RPM. This audio is:
- Processed entirely on your device, in real time, using on-device signal analysis.
- Never recorded to a file, transmitted off your device, uploaded to any server, or shared with any third party.
- Discarded immediately after each analysis window — RPMCalc has no audio storage or history feature.
You can deny or revoke microphone access at any time in iOS Settings > Privacy & Security > Microphone. RPMCalc will simply be unable to take a reading until access is restored.
Information We Do Not Collect
RPMCalc has no account system, no analytics SDK, no advertising SDK, no crash reporting service, and no internet connectivity of any kind. We do not collect your name, email address, location, device identifiers, usage statistics, or any other personal information.
Data Storage
Your engine settings — cylinder count, 2-stroke/4-stroke selection, and Auto-Freeze delay — are saved only in your device's local app storage (iOS UserDefaults / SwiftUI @State), so your preferences persist between sessions on your phone. This data never leaves your device and is deleted automatically if you delete the app.
Safety Disclaimer
- RPMCalc estimates engine speed acoustically from the microphone. It is not a certified or calibrated tachometer.
- Background noise, wind, exhaust modifications, and multiple nearby engines can produce inaccurate readings.
- Do not use this app as the sole basis for safety-critical decisions such as redline limits, tuning, or maintenance timing.
- Always follow your engine or equipment manufacturer's official instrumentation and service guidance.
Children's Privacy
RPMCalc does not knowingly collect any information from anyone, including children under 13, because it does not collect information from anyone at all.
Changes to This Page
If this page ever changes — for example, if a future version of the app adds a feature that does collect data — we will update this page and revise the effective date above.