CPAP pressure refers to the level of air pressure required to keep the upper airways open during sleep. It depends on several individual factors and cannot be the same for every patient.
This page provides an educational CPAP pressure calculator, based on the Hoffstein formula, which has been used in clinical research to estimate a theoretical therapeutic pressure from simple parameters: BMI, neck circumference and apnea–hypopnea index (AHI).
⚠️ Important: this calculator is not a prescription tool and does not replace medical titration or the advice of a sleep specialist.
What is CPAP pressure?
CPAP pressure is the air pressure (expressed in cmH₂O) required to keep the upper airways open during sleep.
Its purpose is to:
- prevent apneas and hypopneas,
- stabilize breathing,
- improve oxygenation and sleep quality.
👉 This pressure is sometimes referred to as therapeutic pressure, target pressure or optimal pressure (depending on CPAP manuals).
Why is CPAP pressure different for each patient?
There is no “standard” CPAP pressure that works for everyone. The required pressure depends on:
- body morphology (weight, neck size),
- severity of sleep apnea,
- sleep position (back / side),
- REM sleep,
- nasal congestion,
- mask leaks.
This is why some patients look for an estimated CPAP pressure for educational purposes, before or after medical follow-up.
Parameters used in the calculation
BMI (Body Mass Index)
BMI reflects the anatomical load on the upper airways. A higher BMI is statistically associated with a higher pressure requirement.
Neck circumference
Neck circumference is an indirect indicator of upper airway size and is commonly used when assessing sleep apnea risk.
AHI (Apnea–Hypopnea Index)
AHI corresponds to the number of respiratory events per hour of sleep, measured during a sleep study. Higher AHI values are generally associated with higher therapeutic pressure needs.
The formula used (Hoffstein)
The calculator below uses a formula published in clinical research to estimate a theoretical CPAP therapeutic pressure based on BMI, neck circumference and AHI.
Formula (estimation):
Pressure (cmH₂O) = 0.16 × BMI + 0.13 × Neck circumference (cm) + 0.04 × AHI − 5.12
👉 This formula provides an indicative value (order of magnitude only). It does not replace titration or medical advice.
Calculate my theoretical CPAP pressure
👉 The result represents an educational estimate based on the Hoffstein formula. It helps understand the approximate pressure range and facilitates discussion with a sleep specialist or sleep clinic.
How should the result be interpreted?
Fixed CPAP
A fixed CPAP delivers a single pressure throughout the night. The estimated value corresponds to a theoretical therapeutic target pressure.
APAP (automatic CPAP)
An APAP automatically adjusts pressure within a minimum and maximum range. The calculator may display a central theoretical value with an indicative range (± 2 cmH₂O).
ℹ️ This range is not a setting recommendation, but an illustration of how automatic devices operate.
Ramp pressure vs therapeutic pressure
- Ramp pressure: low pressure at sleep onset, intended for comfort.
- Therapeutic pressure: effective pressure required to prevent apneas.
👉 The calculator refers only to therapeutic pressure, not ramp settings.
When should you consult or reassess?
Even with appropriate pressure, certain symptoms should prompt medical review:
- persistent daytime sleepiness,
- frequent or non-restorative awakenings,
- snoring while using CPAP,
- significant mask leaks,
- recent weight gain,
- dryness, discomfort or poor adherence.
In such cases, a medical reassessment is recommended.
FAQ – CPAP pressure
What is a normal CPAP pressure?
There is no “normal” pressure. Most treatments fall between 4 and 20 cmH₂O, depending on the individual.
Can I adjust my CPAP using this calculator?
❌ No. This calculator is educational. Any pressure change must be validated by a healthcare professional.
What are the signs of CPAP pressure being too high?
Excessive CPAP pressure may cause discomfort such as:
- significant mask leaks,
- bloating or air swallowing (aerophagia),
- dry mouth or nasal dryness,
- sleep disruption due to discomfort.
👉 These symptoms should be discussed with a healthcare professional.
How can I tell if CPAP pressure is too low?
Insufficient pressure may fail to adequately treat sleep apnea. Possible signs include:
- persistent daytime sleepiness,
- frequent awakenings,
- ongoing snoring while on CPAP,
- elevated residual AHI on follow-up reports.
👉 A medical reassessment is recommended in this case.
Where can I find my AHI?
AHI is reported in your sleep study (polygraphy or polysomnography) and sometimes in CPAP follow-up reports.
What is the difference between CPAP and APAP?
CPAP: fixed pressure.
APAP: automatically adjusts pressure within a defined range.
Conclusion
This CPAP pressure calculator aims to help understand the factors influencing therapeutic pressure and better interpret information related to sleep apnea treatment.
Treatment comfort and effectiveness depend not only on pressure, but also on the equipment used.
👉 Explore our range of CPAP masks and CPAP accessories designed to improve comfort, seal and treatment adherence.