What is the BOLT score?
The BOLT score is the number of seconds you can comfortably hold your breath after a normal breath out, stopping at the first definite urge to breathe. BOLT stands for Body Oxygen Level Test. It’s used as a rough sign of how sensitive you are to carbon dioxide, the gas that mainly drives your urge to breathe.
The test comes from Buteyko breathing practice, where it’s called the control pause, and was popularised by Patrick McKeown through his Oxygen Advantage method. The test measures how soon your body asks for the next breath.
How to do the BOLT test properly
- Sit down and breathe normally through your nose for a minute or two. Patrick McKeown suggests resting for about ten minutes first and testing first thing in the morning. Whatever you choose, keep it the same each time so your scores compare.
- Breathe in normally, then breathe out normally. Don’t take a big breath first, and don’t empty your lungs.
- Pinch your nose and start the timer.
- Stop at the first definite urge to breathe: a swallow, a tug in your throat or belly, or a clear wish to breathe.
- Let go and breathe in through your nose. That breath should be calm. If you gasped, you held too long. Rest for a minute and try again, stopping earlier.
The common mistake is holding on for as long as you can. That turns a gentle check into a breath-hold contest, and the number stops meaning what it’s meant to.
What does your BOLT score mean?
Treat the number as a personal benchmark. Patrick McKeown, who popularised the test, gives this rough guide:
| BOLT score | How he reads it |
|---|---|
| Under 10 seconds | A starting point with plenty of room to improve, often with a lot of sighing and yawning |
| 10 to 20 seconds | Common; a usual starting point for breathing practice |
| 20 to 30 seconds | Typical of people who exercise regularly |
| 40 seconds | His training goal, not a line between healthy and unhealthy |
That’s one practitioner’s guide (opens in new tab), and others draw the lines elsewhere: 25 seconds, 40, even 60 as “excellent”. None of these scales has been validated. Your own trend is the useful number.
The limits of the BOLT score
The BOLT test is easy and free, which is why it’s popular. It also has limits the charts rarely mention.
- There’s no agreed scale. Sites disagree on what “good” means, and none of their charts has been validated.
- The end point is a judgement call. The “first definite urge” is something you decide. Two people, or the same person on two days, will call it differently, and anyone hoping for a higher number tends to hold longer.
- It moves from day to day. Sleep, food, stress, exercise, illness, and the time of day all shift it. One reading is mostly noise.
- The research is thin. A 2024 study of 49 elite speedskaters (opens in new tab) found their BOLT scores weren’t linked to their performance, and its authors note the test hasn’t been validated. It doesn’t diagnose anything, and it isn’t a fitness grade.
- A longer hold doesn’t always mean lower sensitivity. In one study, two weeks of daily breath-holds lengthened people’s holds by almost half (opens in new tab) while their sensitivity to carbon dioxide didn’t change. They got more comfortable with the urge.
- It’s easy to turn into a maximum hold. Chasing a bigger score pushes the test toward breath-hold training, which carries risks of its own.
That’s why this page keeps your scores, shows your trend, and doesn’t grade a single result.
BOLT, CO2 tolerance, and breath-hold training
The BOLT score is one way into a bigger idea, CO2 tolerance: how much carbon dioxide your body lets build up before it pushes you to breathe. Anxiety and habitual over-breathing tend to go with an urge that arrives early, and practitioners often see a low score alongside sighing, yawning, and breaths that never feel full. The CO2 tolerance article explains the physiology, including what the Bohr effect does and doesn’t mean.
The CO2 tolerance test measures something related with no breath-hold at all: how slowly you can breathe out. Freedivers’ CO2 tables are a different thing again: a series of long breath-holds with shrinking rests, sized from your maximum hold. They belong with a freediving instructor.
How to improve your BOLT score
Go slowly and work with your breathing rather than with breath-holds. These are the usual steps:
- Breathe through your nose, at rest and on easy walks.
- Slow down for five to ten minutes a day, to around six breaths a minute. You can use this online coherent breathing timer to follow the right rhythm.
- Breathe smaller. Let each breath become soft and small, until there’s a slight, comfortable hunger for air. This is the idea behind Buteyko’s “breathe light”. Stop if it tips into panic or strain.
- Test once a week at the same time of day and watch the direction over a month or two.
Expect the feeling to change before the number does. People often notice fewer sighs and calmer breathing first.
Is the BOLT test safe?
For most people, yes. It’s a short, comfortable hold, done sitting down, stopping at the first urge.
Safety
- Hold only until the first urge to breathe. Never push for a longer hold.
- Never test in water, near water, or while driving.
- Skip it if you're pregnant or have a heart or lung condition. Use coherent breathing instead, which has no holds.
- If you feel dizzy or unwell, stop and breathe normally.
More on this in breathwork safety and contraindications.