Observed arrival · 2026-11-09
RPM Counter, a microphone tachometer
A browser-based tool that estimates engine RPM from a phone microphone, with settings for different engine types and rotating equipment.
- For
- People checking engines, fans, drones, or other rotating equipment
- Worth noticing
- The FAQ gives separate frequency formulas for four-stroke and two-stroke engines and warns about wind and low-bass filtering.
Field notes
The page exposes controls for four-stroke, two-stroke, rotary, fan/propeller, and custom inputs, with cylinder, rotor, or blade counts and selectable RPM ranges. Its FAQ gives separate frequency-to-RPM formulas for four-stroke and two-stroke engines, and explains that wind, nearby engines, and microphone bass filtering can affect readings. The community area currently says there are no sessions; submitted sessions may include a nickname, notes, and city or country derived from IP.
Observed signals
Read the marks
Editorial observations of this landing page, not a rating.
One card from the complete issue