Oxygen Content in Blood

Blood Oxygen Content Calculator

CxO₂ = (1.36 × Hb × SxO₂) + (0.0031 × PxO₂)  ·  ATS/ERS 2022 · ESC 2024

CaO₂ / CvO₂

Full equation: CxO2 = (1.36 × Hb × SxO2/100) + (0.0031 × PxO2)  ·  Unit: mL O2/dL blood (vol%)

Hb-bound: 1.36 mL O2/g Hb (Hüfner constant)  ·  Dissolved: 0.0031 mL O2/mmHg/dL (solubility coefficient)

Normal CaO₂: 17–21 mL/dL  ·  Normal CvO₂: 12–15 mL/dL  ·  a–v diff (C(a–v)O₂): 4–6 mL/dL

Clinical presets

Please enter valid values for all required fields.

Arterial blood gas values

PaO₂

mmHg

Arterial O₂ partial pressure · ABG · Normal: 80–100 mmHg

SaO₂

%

Arterial O₂ saturation · ABG or pulse oximetry · Normal: 95–100%

Hb (arterial)

g/dL

From CBC / FBC · Normal: M 13–17, F 12–16 g/dL

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Venous blood gas values (PA catheter or central line)

PvO₂

mmHg

Mixed venous O₂ partial pressure · PA catheter · Normal: 35–45 mmHg

SvO₂

%

Mixed venous saturation · PA catheter · Normal: 70–75% · Critical: <50%

Hb (venous)

g/dL

Usually same as arterial · Enter if different from arterial sample

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Blood Oxygen Content

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—

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O₂ content breakdown — Hb-bound vs dissolved

Hb-bound (1.36×Hb×S)

18.0 mL/dL (97%)

Dissolved (0.0031×P)

0.28 mL/dL (3%)

Total CxO₂

18.3 mL/dL

CaO₂ — Arterial

—

mL O₂ / dL blood

CvO₂ — Venous

—

mL O₂ / dL blood

C(a–v)O₂ — Arteriovenous O₂ content difference

— mL/dL

Normal: 4–6 mL/dL  ·  ↑ with low CO  ·  ↓ in distributive shock

Hb-bound O₂

—

mL/dL (dominant)

Dissolved O₂

—

mL/dL (minor)

Dissolved %

—

of total CxO₂

Blood oxygen content — clinical reference values

Blood type	CxO2 (mL/dL)	Hb-bound	Dissolved	Clinical note
Normal arterial (CaO2)	17 – 21	~97–98%	~2–3%	PaO2 80–100, SaO2 95–100%, Hb 12–17 g/dL
Normal venous (CvO2)	12 – 15	~97%	~1–2%	PvO2 35–45, SvO2 70–75%, same Hb
Normal a–v difference	4 – 6	—	—	C(a–v)O2; reflects tissue O2 extraction at rest
Anaemia (Hb 7 g/dL)	~9 – 10	~97%	~3%	Reduced capacity; compensated by ↑ CO and ↑ O2ER
Hyperbaric O2 (3 ATA)	~20 – 25	~85%	~15%	Dissolved O2 increases dramatically; can sustain life without Hb

CxO₂ = (1.36 × Hb × SxO₂/100) + (0.0031 × PxO₂)  ·  Hüfner constant 1.36 mL O₂/g Hb  ·  Solubility 0.0031 mL/mmHg/dL  ·  No patient data stored or transmitted

Clinical references

• 1.Hüfner CG. Über das Gesetz der Dissociation des Oxihämoglobins und seine Bedeutung für die Physiologie. Arch Anat Physiol. 1890;1–27. (Hüfner constant — 1.36 mL O₂/g haemoglobin)
• 2.Henry W. Experiments on the quantity of gases absorbed by water, at different temperatures, and under different pressures. Philos Trans R Soc Lond. 1803;93:29–274. (Henry's law — basis of dissolved O₂ coefficient 0.0031 mL/mmHg/dL)
• 3.McLellan SA, Walsh TS. Oxygen delivery and haemoglobin. Contin Educ Anaesth Crit Care Pain. 2004;4(4):123–126. doi:10.1093/bjaceaccp/mkh033 (CaO₂, CvO₂, DO₂, and VO₂ framework)
• 4.Vincent JL, De Backer D. Oxygen transport — the oxygen delivery controversy. Intensive Care Med. 2004;30(11):1990–1996. doi:10.1007/s00134-004-2419-4 (Oxygen content and delivery relationship in critical care)
• 5.Lumb A. Nunn's Applied Respiratory Physiology. 9th ed. Elsevier; 2020. (Comprehensive chapter on blood oxygen transport, CaO₂ calculation, and oxygen-haemoglobin dissociation)
• 6.West JB, Luks AM. West's Respiratory Physiology: The Essentials. 10th ed. Wolters Kluwer; 2016. (O₂ carriage in blood: Hb-bound vs dissolved fraction)
• 7.Boyle RL. Hyperbaric oxygen therapy and dissolved oxygen. Diving Hyperb Med. 2021;51(1):1–8. (Dissolved O₂ significance at hyperbaric pressures — Boyle's law and Henry's law interaction)
• 8.Squara P. Matching total body oxygen consumption and delivery: a crucial objective? Intensive Care Med. 2004;30(12):2170–2179. (C(a–v)O₂ and the Fick principle in supply-demand mismatch)
• 9.Rivers E, Nguyen B, Havstad S, et al. Early goal-directed therapy in severe sepsis and septic shock. N Engl J Med. 2001;345(19):1368–1377. (Role of CvO₂/SvO₂ as resuscitation targets and oxygen content interpretation)

Frequently asked questions

Medical disclaimer

For qualified clinical professionals only. This Blood Oxygen Content Calculator is an educational decision-support tool. It does not replace arterial or venous blood gas interpretation, haematological assessment, or comprehensive haemodynamic evaluation by a qualified clinician.

The Hüfner constant used in this calculator is 1.36 mL O₂/g haemoglobin — the widely accepted clinical standard. The theoretical maximum is 1.39 mL O₂/g (assuming 100% O₂ binding by pure haemoglobin A), and some sources use 1.34 mL O₂/g to account for methaemoglobin and carboxyhaemoglobin. In the presence of significant dyshemoglobinaemia (COHb >5%, MetHb >2%), the effective O₂-carrying capacity is reduced and this calculator's result will overestimate actual CaO₂.

The dissolved O₂ coefficient (0.0031 mL O₂/mmHg/dL blood at 37°C) is derived from Henry's law for O₂ solubility in plasma at body temperature. This fraction is normally trivial (<3% of total CaO₂) but becomes clinically significant in hyperbaric oxygen therapy (100% O₂ at 3 ATA can provide sufficient dissolved O₂ to sustain life without haemoglobin).

SaO₂ from pulse oximetry (SpO₂) may overestimate true SaO₂ from ABG in the presence of dyshemoglobinaemia, poor peripheral perfusion, nail polish, and severe anaemia. For accurate CaO₂ calculation, use co-oximetry-derived SaO₂ from arterial blood gas analysis. This tool does not store or transmit patient data.

Last reviewed: January 2026  ·  Hüfner 1890  ·  Henry's law 1803  ·  Nunn's Applied Respiratory Physiology 9th ed.  ·  West's Respiratory Physiology 10th ed.  ·  ATS/ERS 2022