Oxygen Content Calculator
CaO₂ from hemoglobin, saturation and the dissolved trace — the arithmetic that shows why the hemoglobin count, not the saturation, sets what the blood carries.
Oxygen Content Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Arterial side only; no mixed-venous path
- Hüfner convention quoted approximate
In short: Blood with a hemoglobin of 15 g/dL, a saturation of 97% and a PaO₂ of 95 mmHg carries 19.782000 mL of oxygen per dL: 19.497000 of it bound to hemoglobin and just 0.285000 dissolved in the plasma — the dissolved trace is about 1.4% of the cargo. At a cardiac output of 5 L/min that is a delivery of 989.100000 mL/min. The split is the lesson: PaO₂ — the number pulse-oximeter talk centres on — prices only the trace; the hemoglobin multiplier owns the cargo.
Formula
CaO₂ = (1.34 × Hb × SaO₂) + (0.003 × PaO₂) ··· DO₂ = CaO₂ × CO × 10
Each gram of hemoglobin carries about 1.34 mL of oxygen when fully saturated — Hüfner’s measured figure; the idealized 1.36 is quoted in some texts, an approximate convention either way. The 0.003 solubility coefficient prices the plasma’s dissolved trace from PaO₂. Delivery multiplies content by cardiac output, with the ×10 converting dL to litres.
Worked Example
- Enter hemoglobin and saturation.
- Enter PaO₂ for the dissolved trace.
- Read the content and the bound-versus-dissolved split.
- Add cardiac output for the delivery figure.
Defaults: Hb 15, 97%, 95 mmHg, CO 5 → CaO₂ 19.782000, DO₂ 989.100000 mL/min. Drop the hemoglobin to 10 on the same gases → 13.283000 — the content falls a third while the saturation never moved. Hyperbaric flourish: PaO₂ 300 dissolves 0.900000 mL/dL, still small.
Strengths & Limits Of This Model
Where this engine is strong
- The bound/dissolved split is explicit
- Delivery priced from the same panel
Where it stops
- No P50 or oxyhemoglobin curve
- No extraction-ratio arithmetic
Practical Use Cases
Critical care
content over saturation
Anemia grading
what the count does to delivery
Teaching
the trace versus the cargo
Methodology & Editorial Standards
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Oxygen Content Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
Why 1.34 and not 1.36?
Hüfner’s constant has two published values: the idealized stoichiometry gives 1.36 mL per gram, the measured capacity of real blood comes out near 1.34 because a sliver of hemoglobin is methemoglobin or carboxyhemoglobin and cannot carry. This page uses 1.34, the convention most clinical texts print; the difference is under two percent and both are quoted approximate.
Why does the saturation barely matter next to hemoglobin?
Because the saturation multiplies only the bound fraction, while hemoglobin sets how much binder exists at all. A patient whose hemoglobin falls from 15 to 10 loses a third of the cargo with the saturation untouched; a patient desaturating from 97 to 88 percent loses under a tenth. The dissolved term is tinier still — which is why transfusion changes content in a way oxygen therapy alone cannot when the count is low.
What is the dissolved term for, then?
It is small at room air but it is the only part of the cargo that is physically free in the plasma, and it scales linearly with PaO₂ — which is exactly why hyperbaric oxygen can deliver meaningful oxygen with no hemoglobin at all, and why the dissolved trace grows tenfold under hyperbaric conditions. The card prints its share so the scale stays honest.
Is DO₂ the same as VO₂?
No — delivery is what the pump offers, consumption is what the tissues take, and their difference is the extraction reserve. This page prices delivery only; consumption needs the mixed-venous side of the same arithmetic. Rising extraction, falling delivery — that story belongs to the team and the monitor, not the formula alone.
Can I enter SpO₂ from the pulse oximeter?
Yes, as an estimate — the peripheral reading approximates SaO₂ well in most patients and badly in poor perfusion, dyshemoglobinemias and some poisonings. The page computes with whatever saturation it is given; it cannot know the probe was reading nail polish.
If the dissolved term is trivial, why does the tension matter at all?
Two reasons — it is the pressure gradient that drives oxygen into tissues, and it is the number hypoxemia symptoms and ventilator decisions track. The content page prices cargo; the tension prices delivery pressure. A patient can carry a full cargo at a tension that still cannot push it across a shunt.
What is the arterial-venous difference for?
It is the consumption side — the same formula run on a mixed-venous sample, and the difference between the two is what the tissues actually extracted. This page prices the arterial half; the extraction story needs the venous draw and the team that reads it.
Do abnormal hemoglobins change the arithmetic?
They change its meaning — carboxyhemoglobin and methemoglobin bind without carrying usefully, and the pulse oximeter reads them as ordinary saturation. The 1.34 multiplier assumes working hemoglobin; in dyshemoglobinemias the content computed here flatters a blood that cannot deliver it.