The BOLT test (Body Oxygen Level Test) is the simplest way to find out how efficiently you breathe. It takes less than a minute, and all you need is a clock — the result tells you more about your resilience, your sleep and your endurance than most people expect. Take the test right here:
The BOLT Test: How Efficient Is Your Breathing?
The BOLT test (Body Oxygen Level Test) measures in seconds how your body responds to CO₂ ‐ the best simple indicator of your breathing efficiency. All you need is a timer: it is built in below.
- Sit upright and take a few calm breaths through your nose.
- Take a normal breath in and out through your nose.
- After exhaling, pinch your nose and start the timer.
- Stop at the FIRST clear urge to breathe ‐ not your maximum. Swallowing, diaphragm tension or the desire to breathe count as the signal.
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What does your score mean?
Enter your details and you will instantly see your full breakdown: what your score says about stress, sleep and performance ‐ and which training improves it.
Your full breakdown
| BOLT score | What it means | Recommendation |
|---|---|---|
| under 10 | Strongly reduced breathing efficiency ‐ your breathing centre reacts very early to CO₂ | Daily light nasal breathing training, no intense breath work yet |
| 10-19 | Reduced ‐ typical with stress, mouth breathing or poor sleep | Functional breathing training focused on light, slow breathing |
| 20-29 | Moderate ‐ solid base, room to improve under load | CO₂ tolerance training and breathing patterns under exertion |
| 30-39 | Good ‐ efficient breathing at rest | Performance-oriented training: breath holds in movement |
| 40+ | Excellent ‐ high CO₂ tolerance | Maintain and apply sport-specifically |
Important: The BOLT score measures your own progress ‐ test in the morning right after waking for the most reliable value, and compare yourself with yourself, not with others.
Why CO2 Tolerance Decides Your Performance
Most people think breathing is about oxygen. In reality, it's CO2 that controls when you feel the urge to breathe. Low CO2 tolerance means you breathe too much and too fast — and paradoxically, less oxygen reaches your tissues as a result. Higher CO2 tolerance means calmer breathing, better oxygen delivery, more endurance and deeper sleep. If you want to go deeper, read why air hunger is the key to better breathing.
How to Improve Your BOLT Score
Your score improves through consistent nasal breathing in daily life and sport, gentle breath holds, and slow, reduced breathing — not more air, but less. You'll find a structured collection of exercises on our exercise page with the BOLT hub. The article 3 Breathwork Techniques That Actually Change Your Physiology explains the key techniques in more depth. If you want guided support to raise your score, the personal breathing program is the right place.
FAQ
What's a good BOLT score?
20 seconds or more is considered good functional breathing. Above 30 seconds is very good. Most people start out between 10 and 20 seconds.
How often should I do the BOLT test?
Best first thing in the morning after waking up, once or twice a week, under the same conditions.
How quickly can I improve my BOLT score?
With daily breath training, your score often rises by several seconds within four to six weeks.
Does the BOLT test measure how long I can hold my breath?
No. You stop at the first urge to breathe, not at your limit.
Want to know what your score means for you? Book a free intro call: cal.com/michael-schnekenburger/30min
Michael Schnekenburger, certified Oxygen Advantage® Advanced Instructor, Atemstark Zurich