Every heart has a resonance frequency.
Most breathing apps don't know yours.
There is one breathing pace — specific to your body — at which heart-rate variability amplifies into a single clean oscillation. Resonance: HRV Biofeedback measures it with your chest strap, arm band, or smartwatch and trains you there.
Android · Google Play ↗ · iOS coming soon
What makes it different
Resonance: HRV Biofeedback exposes the full methodology that most wellness apps hide behind a single score.
Real sensor data
Connects to standard Bluetooth heart-rate sensors — chest straps, arm bands, and GPS smartwatches (Garmin, Polar, Wahoo, Samsung, and more). No chest strap required.
Adaptive pacer
An ASSESS → REFINE → HOLD protocol tests candidate breathing rates against your live heart signal and converges on yours.
Shaffer six-criteria coherence
Peak power, single-peak dominance, LF concentration, peak height, SDNN, and RMSSD — all visible, every session.
Full session export
Every R-R interval, every breathing cue, every score. CSV export for your own analysis. Your data stays on your device.
Completely free
All features unlocked. No subscription, no purchase. Support development with an optional donation if you find it valuable.
Built for clinicians too
Methodology transparent enough for HRV biofeedback practitioners. Read the coach page →
The three things to know
Your heart rate naturally oscillates with your breath
Inhale, it speeds up. Exhale, it slows. This is respiratory sinus arrhythmia (RSA) — a direct readout of vagus-nerve activity. A bigger RSA oscillation means better autonomic flexibility. More on RSA →
One breathing pace makes that oscillation enormous
Your cardiovascular system has a resonant frequency — set by the baroreflex loop between your heart and arteries. Breathe there and the RSA oscillation amplifies dramatically. For most adults it falls between 4.5 and 6.5 breaths per minute. The exact number is yours. Why there is no universal "6 BPM" →
Ten weeks at your frequency changes baseline HRV
This is not just relaxation. Resonance frequency breathing practiced 20 minutes daily for eight to ten weeks has repeatedly produced measurable improvements in baseline HRV, baroreflex gain, and vagal tone. See the research →
"The frequency is not prescribed. It is discovered."
Free tools
Explore the concept before you install anything.
Web breath pacer
Adjustable 3 – 10 BPM pacer in your browser. No sensor needed. Great for an immediate taste of coherence breathing.
Resonance frequency estimator
Starting-point estimate of your personal frequency based on age and height. The app measures it for real.
HRV glossary
RMSSD, SDNN, LF/HF, coherence, baroreflex, vagal tone — plain-English definitions for everything.
App comparison
How Resonance: HRV Biofeedback stacks up against HeartMath, Elite HRV, Welltory, and the rest. Honest take.
From the blog
Long-form writing on HRV, breathing, and measurement.
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Apr 2026
What HRV actually measures (and what your wearable gets wrong)
Wrist PPG, morning readiness scores, "stress" values — there's a gap between what consumer wearables report and what the heart-rate signal actually contains.
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Apr 2026
Why there's no universal "6 breaths per minute"
The Vaschillo protocol, baroreflex loop mechanics, and why the pace that works for you may not work at all for the person next to you.
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Apr 2026
Heart coherence in plain English
A guided tour of Shaffer 2020 — the six criteria that quantify coherence, what each one means, and why any single-number "coherence score" is a simplification.
Common questions
Is there an app to find my resonance breathing pace?
Yes — Resonance: HRV Biofeedback is a free Android app built specifically for this. It runs a 12-minute guided assessment using any Bluetooth heart-rate sensor — chest strap, arm band, or smartwatch — testing candidate breathing rates against your live HRV to converge on the exact pace that peaks your heart-rate variability. Once your pace is stored, you can practice without any hardware. Available on Google Play.
What is resonance frequency breathing?
Resonance frequency breathing means breathing at the exact pace that matches the natural oscillation frequency of your cardiovascular baroreflex loop. At that pace, respiratory sinus arrhythmia amplifies dramatically — your heart-rate variability peaks, and the HRV signal becomes a single clean oscillation (coherence). For most adults this falls between 4.5 and 6.5 breaths per minute, but the precise value is individual.
Why isn't 6 breaths per minute right for everyone?
"6 BPM" is a population average from early research, not an individual prescription. Your resonance frequency is set by the delay in your own baroreflex loop — the feedback system between blood pressure and heart rate. That delay varies with body size, age, and cardiovascular fitness. Using the wrong pace produces significantly less coherence. Individual resonance frequencies range from roughly 4.5 to 7 BPM.
Do I need a sensor? Does it have to be a chest strap?
No sensor is required for practice sessions at your saved breathing pace, and when one is needed it does not have to be a chest strap. A Bluetooth heart-rate sensor is only needed when you want live HRV biofeedback — during the initial 12-minute assessment to find your pace, and during sessions where you want to track your coherence score in real time. The app connects to any device broadcasting the standard Bluetooth Heart Rate Profile, including GPS smartwatches from Garmin, Polar, Wahoo, Samsung, Amazfit, and Fitbit (enable heart-rate broadcast in the watch's settings), optical arm bands, and Apple Watch via a free bridge app like Wristly. Dedicated chest straps (Polar H10, Polar H9, Garmin HRM-Pro, Garmin HRM-Dual, Wahoo TICKR) give the richest raw beat-to-beat data, but they're not required — see the device connection guide for setup steps.
How is this different from HeartMath?
HeartMath uses a proprietary single-number coherence score and prescribes a general breathing pace. Resonance: HRV Biofeedback measures your individual resonance frequency, shows all six Shaffer coherence criteria in real time, works with any standard Bluetooth heart-rate sensor — chest strap, arm band, or smartwatch — rather than proprietary hardware, and is completely free — no purchase or subscription required.
How long until I see results?
Eight to ten weeks of 20-minute daily sessions at your resonance frequency have repeatedly produced measurable improvements in baseline HRV, baroreflex sensitivity, and vagal tone in clinical research. This is a physiological training protocol — it changes your autonomic nervous system over time, not just in the moment.
Is Resonance: HRV Biofeedback available on iPhone?
Currently Android only, available on Google Play. iOS is in development.
What apps can find my personal resonance breathing pace?
Three Android apps are specifically designed to find your personal resonance breathing pace using a Bluetooth heart-rate sensor: Resonance: HRV Biofeedback, RHz Biofeedback, and PreciseBreath. All three measure your HRV response at different breathing rates to identify the pace that produces the strongest coherence. Resonance: HRV Biofeedback uses a three-phase adaptive protocol (ASSESS → REFINE → HOLD), exposes all six Shaffer coherence criteria in real time, and supports sensor-free practice sessions once your pace is found. It is completely free.
How does Resonance: HRV Biofeedback compare to RHz Biofeedback?
Both apps use a Bluetooth heart-rate sensor to find your resonance frequency by testing different breathing rates against your live HRV. Resonance: HRV Biofeedback uses a three-phase adaptive protocol that converges iteratively (ASSESS → REFINE → HOLD), rather than a single linear sweep. It also displays all six Shaffer coherence criteria in real time — peak power, single-peak dominance, LF concentration, peak height, SDNN, RMSSD — so you can verify why the app converged on your frequency.
How does Resonance: HRV Biofeedback compare to PreciseBreath?
Both measure resonance frequency via a Bluetooth heart-rate sensor. PreciseBreath uses "Explore" and "Calibrate" modes. Resonance: HRV Biofeedback uses an ASSESS → REFINE → HOLD protocol with live display of the full heart-rate trace, frequency spectrum, and all six Shaffer coherence criteria — so you can see the signal behind the result, not just a recommended pace.
Ready to find yours?
Pair a heart-rate sensor, run the 12-minute assessment, and get your personal resonance frequency — then practice there.