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The Rythmo respiratory rate apps

The same tap-per-breath engine on four platforms, written from the published method (Karlen et al 2014). Tap once per breath and read the rate per minute.

iPhone and Apple Watch: free on the App Store. Android: free on Google Play. Garmin: free on the Connect IQ Store.

Concept render of an iPhone running the Rythmo app, reading 20 per minute, Confident, after 6 taps in 16 seconds, with the reference range table belowConcept render. The screen matches the app.

iPhone

A large tap surface carries the rate, so the number sits where your thumb lands and your eyes stay on the chest. It counts the moment your finger touches down, so quick or sliding taps still register. Reset runs the full width below it, where it cannot be hit while tapping.

Three tabs. Measure shows the rate, the confidence indicator, tap count, elapsed time and the reference range table. History keeps your last 10 readings. Info covers how to use the app, its limitations, the evidence base, the range source, the disclaimer and a switch for vibration on each tap.

Minimum
iOS 17
Status
Out now, free on the App Store

Free, with no in-app purchase. The Apple Watch app comes with it.

Download on the App Store
Concept render of an Apple Watch running the Rythmo app, reading 20 per minute with a confident tick, 6 taps, 16 secondsConcept render. The screen matches the app.

Apple Watch

Runs on its own, with no iPhone nearby, and keeps its own history. The whole screen is the tap target, and Reset sits at the top of the screen, out of the way of your taps.

Swipe between three pages: Measure, Ranges and History. The History page carries the disclaimer and points here for full instructions, so the how to use, limitations and evidence sections below are the watch app's instructions too. It installs alongside the iPhone app.

Minimum
watchOS 10
Status
Out now, free with the iPhone app

One download covers both. Installing the iPhone app puts the watch app on your Apple Watch.

Download on the App Store
Concept render of an Android phone running the Rythmo app, reading 20 per minute, Settling, after 3 taps in 7 seconds, with the reference range table belowConcept render. The screen matches a test build.

Android

The same dark design and the same engine as the iPhone app. The tap surface counts the moment your finger touches down, Reset runs the full width below it, and the Measure, History and Info tabs match the iPhone app, including the switch for vibration on each tap.

Minimum
Android 8.0 (API level 26)
Status
Out now, free on Google Play

Free, with no in-app purchase.

Get it on Google Play
Concept render of two round sports watches running the Rythmo Garmin app, one reading 20 per minute with three confidence pips after 6 taps in 16 seconds, the other showing History with two readings of 20 per minuteConcept render. The screen matches a test build.

Garmin

Tap the screen or press the start key once per breath. Taps are silent. Measure shows the rate, three confidence pips, the tap count and elapsed time, with an Irregular label when the gaps keep varying.

Open the menu for Reset, History and Clear history. The Garmin app has two screens, Measure and History, and shows no reference ranges, to keep it simple and working on as many watches as possible. The disclaimer below applies to it.

Works on these Garmin watches:

  • Approach S50, S70
  • D2 Air, Air X10, Delta, Delta PX, Delta S, Mach 1, Mach 2, Mach 2 Pro
  • Descent G1, G2, Mk1, Mk2, Mk2 S, Mk3
  • Enduro, Enduro 3
  • epix (Gen 2), epix Pro (Gen 2)
  • fenix 5, 5 Plus, 5S, 5S Plus, 5X, 5X Plus, Chronos
  • fenix 6, 6 Pro, 6S, 6S Pro, 6X Pro
  • fenix 7, 7 Pro, 7S, 7S Pro, 7X, 7X Pro
  • fenix 8, 8 Pro, 8 Solar, fenix E
  • fenix 9, 9 Pro, 9 Pro Solar
  • Forerunner 55, 70, 165, 170, 245, 255, 255S, 265, 265S, 570, 645, 745, 935, 945, 945 LTE, 955, 965, 970, and their Music editions
  • Instinct 2, 2S, 2X, 3, 3 AMOLED, E, Crossover, Crossover AMOLED
  • MARQ, MARQ (Gen 2)
  • Venu, Venu 2, 2 Plus, 2S, 3, 3S, 4, Sq, Sq 2, X1
  • vivoactive 3, 4, 4S, 5, 6
  • Legacy Hero and Legacy Saga series
  • quatix and tactix editions of the fenix and epix models above
Minimum
Connect IQ 3.1
Status
Free on the Connect IQ Store

Free, with no in-app purchase.

Get it on the Connect IQ Store

How to use

  1. Watch the chest. Tap once for every breath you see. The first tap is breath one.
  2. A rate appears from the second tap and sharpens with every tap after it. Keep tapping until the indicator reads Confident.
  3. Press Reset to finish. Measurements of 3 taps or more are saved to History automatically, including when the app closes mid-count.

On a Garmin watch, use Reset in the menu to finish.

Reading the confidence indicator

  • Red, Low confidence. Not enough consistent taps yet. Treat the number as a rough early figure.
  • Amber, Settling. The pattern is building.
  • Green, Confident. Enough consistent taps. Green needs 5 valid taps, plus one more for every 10 per minute above 30, because faster rates need more taps for the same precision.

What counts as a valid tap

A valid tap is one whose gap sits within 13% of the running median. Gaps outside that are left out of the calculation, so one mistimed tap does not throw the result. If 3 taps in a row are rejected, Rythmo starts a fresh baseline from your recent taps.

From 10 taps, if the gaps keep varying, an Irregular label appears and the indicator will not go above amber.

Limitations

  • The rate is calculated from your taps, so it is only as good as your observation of each breath.
  • An Irregular flag means the intervals between your taps vary widely. The displayed rate is the median and may not represent an irregular pattern well.
  • Confidence reflects tap consistency, not clinical accuracy.

Evidence base

Tap-per-breath counting takes the intervals between your taps, uses the median interval, and converts it to a rate per minute. The method is described in the peer reviewed literature, beginning with Karlen and colleagues (PLoS One 2014;9(6):e99266) and the RRate app. Rythmo is written from the published description of that method.

Karlen W, Gan H, Chiu M, Dunsmuir D, Zhou G, Dumont GA, Ansermino JM. Improving the accuracy and efficiency of respiratory rate measurements in children using mobile devices. PLoS One. 2014;9(6):e99266. doi.org/10.1371/journal.pone.0099266

The reseeding after 3 rejected taps, the rate-adjusted green threshold and the Irregular cap are Rythmo additions.

The full evidence, including where the method falls down

Reference ranges

The iPhone, Apple Watch and Android apps show published respiratory rate reference ranges for seven age bands, all at once: 0 to 24 hours, under 3 months, 3 to 12 months, 1 to 4 years, 5 to 11 years, 12 to 15 years, and 16 years and over. A band shows green when the current rate is inside it and red when it is not. The source is cited on the same screen as the table. Rythmo does not interpret the result. The Garmin app and this website show no reference ranges.

Disclaimer

Rythmo is a reference and training tool. It reports a rate calculated from your own taps and displays published reference ranges for comparison. It does not diagnose, does not decide treatment, and does not replace your clinical assessment. Confirm every reading before you act on it or document it.

For medical advice, diagnosis or treatment, consult a qualified healthcare professional.

Privacy

The apps have no accounts, no analytics and send nothing. Readings stay on your device. Full details are in the privacy policy.

Help

See Support, or email hello@rythmo.com.au.