A-a Gradient Calculator

This advanced calculator is designed for healthcare professionals to compute the alveolar-arterial (A-a) gradient, an important measure for assessing lung function.

Calculator

Partial Pressure of Oxygen (PaO2) *

Fraction of Inspired Oxygen (FiO2) *

Partial Pressure of Carbon Dioxide (PaCO2) *

Results

A-a Gradient: N/A

Data Source and Methodology

This calculator uses standard formulas for the A-a gradient based on medical research. View full details.

All calculations are based strictly on these formulas and data provided by this source.

The Formula Explained

The A-a gradient is calculated as follows:

A-a Gradient = (FiO2 × (760 - 47) - (PaCO2 / 0.8)) - PaO2

Glossary of Terms

PaO2: Partial pressure of oxygen in arterial blood.
FiO2: Fraction of inspired oxygen.
PaCO2: Partial pressure of carbon dioxide in arterial blood.

How It Works: A Step-by-Step Example

Consider a patient with PaO2 of 85 mmHg, FiO2 of 0.21, and PaCO2 of 40 mmHg. The A-a gradient can be calculated as follows:

A-a Gradient = (0.21 × (760 - 47) - (40 / 0.8)) - 85 = 10.7 mmHg

Frequently Asked Questions (FAQ)

What is the A-a gradient used for?

The A-a gradient is used to identify issues with oxygen transfer from the alveoli to the blood.

Is a higher A-a gradient concerning?

Yes, a higher A-a gradient may indicate issues such as pulmonary embolism or fibrosis.

Can this calculator be used for all patients?

This calculator is intended for healthcare professionals and may not be suitable for all patient situations.

What units should be used?

PaO2 and PaCO2 should be entered in mmHg, and FiO2 as a decimal (e.g., 0.21 for 21%).

How often should the A-a gradient be checked?

The frequency depends on the clinical scenario; consult with a healthcare provider for guidance.

Audit: Complete

Formula (LaTeX) + variables + units

This section shows the formulas used by the calculator engine, plus variable definitions and units.

Formula (extracted LaTeX)

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Variables and units

No variables provided in audit spec.

Sources (authoritative):

View full details. — mdcalc.com · Accessed 2026-01-19
https://www.mdcalc.com/calc/243/a-a-o2-gradient

Changelog

Version: 0.1.0-draft
Last code update: 2026-01-19

0.1.0-draft · 2026-01-19

Initial audit spec draft generated from HTML extraction (review required).
Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
Confirm sources are authoritative and relevant to the calculator methodology.

Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn

, ', svg: { fontCache: 'global' } };

A-a Gradient Calculator

This advanced calculator is designed for healthcare professionals to compute the alveolar-arterial (A-a) gradient, an important measure for assessing lung function.

Calculator

Partial Pressure of Oxygen (PaO2) *

Fraction of Inspired Oxygen (FiO2) *

Partial Pressure of Carbon Dioxide (PaCO2) *

Results

A-a Gradient: N/A

Data Source and Methodology

This calculator uses standard formulas for the A-a gradient based on medical research. View full details.

All calculations are based strictly on these formulas and data provided by this source.

The Formula Explained

The A-a gradient is calculated as follows:

A-a Gradient = (FiO2 × (760 - 47) - (PaCO2 / 0.8)) - PaO2

Glossary of Terms

PaO2: Partial pressure of oxygen in arterial blood.
FiO2: Fraction of inspired oxygen.
PaCO2: Partial pressure of carbon dioxide in arterial blood.

How It Works: A Step-by-Step Example

Consider a patient with PaO2 of 85 mmHg, FiO2 of 0.21, and PaCO2 of 40 mmHg. The A-a gradient can be calculated as follows:

A-a Gradient = (0.21 × (760 - 47) - (40 / 0.8)) - 85 = 10.7 mmHg

Frequently Asked Questions (FAQ)

What is the A-a gradient used for?

The A-a gradient is used to identify issues with oxygen transfer from the alveoli to the blood.

Is a higher A-a gradient concerning?

Yes, a higher A-a gradient may indicate issues such as pulmonary embolism or fibrosis.

Can this calculator be used for all patients?

This calculator is intended for healthcare professionals and may not be suitable for all patient situations.

What units should be used?

PaO2 and PaCO2 should be entered in mmHg, and FiO2 as a decimal (e.g., 0.21 for 21%).

How often should the A-a gradient be checked?

The frequency depends on the clinical scenario; consult with a healthcare provider for guidance.

Audit: Complete

Formula (LaTeX) + variables + units

This section shows the formulas used by the calculator engine, plus variable definitions and units.

Formula (extracted LaTeX)

\[','\]

','

Variables and units

No variables provided in audit spec.

Sources (authoritative):

View full details. — mdcalc.com · Accessed 2026-01-19
https://www.mdcalc.com/calc/243/a-a-o2-gradient

Changelog

Version: 0.1.0-draft
Last code update: 2026-01-19

0.1.0-draft · 2026-01-19

Initial audit spec draft generated from HTML extraction (review required).
Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
Confirm sources are authoritative and relevant to the calculator methodology.

Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn

]], displayMath: [['\\[','\\]']] }, svg: { fontCache: 'global' } };, svg: { fontCache: 'global' } };

A-a Gradient Calculator

This advanced calculator is designed for healthcare professionals to compute the alveolar-arterial (A-a) gradient, an important measure for assessing lung function.

Calculator

Partial Pressure of Oxygen (PaO2) *

Fraction of Inspired Oxygen (FiO2) *

Partial Pressure of Carbon Dioxide (PaCO2) *

Results

A-a Gradient: N/A

Data Source and Methodology

This calculator uses standard formulas for the A-a gradient based on medical research. View full details.

All calculations are based strictly on these formulas and data provided by this source.

The Formula Explained

The A-a gradient is calculated as follows:

A-a Gradient = (FiO2 × (760 - 47) - (PaCO2 / 0.8)) - PaO2

Glossary of Terms

PaO2: Partial pressure of oxygen in arterial blood.
FiO2: Fraction of inspired oxygen.
PaCO2: Partial pressure of carbon dioxide in arterial blood.

How It Works: A Step-by-Step Example

Consider a patient with PaO2 of 85 mmHg, FiO2 of 0.21, and PaCO2 of 40 mmHg. The A-a gradient can be calculated as follows:

A-a Gradient = (0.21 × (760 - 47) - (40 / 0.8)) - 85 = 10.7 mmHg

Frequently Asked Questions (FAQ)

What is the A-a gradient used for?

The A-a gradient is used to identify issues with oxygen transfer from the alveoli to the blood.

Is a higher A-a gradient concerning?

Yes, a higher A-a gradient may indicate issues such as pulmonary embolism or fibrosis.

Can this calculator be used for all patients?

This calculator is intended for healthcare professionals and may not be suitable for all patient situations.

What units should be used?

PaO2 and PaCO2 should be entered in mmHg, and FiO2 as a decimal (e.g., 0.21 for 21%).

How often should the A-a gradient be checked?

The frequency depends on the clinical scenario; consult with a healthcare provider for guidance.

Audit: Complete

Formula (LaTeX) + variables + units

This section shows the formulas used by the calculator engine, plus variable definitions and units.

Formula (extracted LaTeX)

\[','\]

','

Variables and units

No variables provided in audit spec.

Sources (authoritative):

View full details. — mdcalc.com · Accessed 2026-01-19
https://www.mdcalc.com/calc/243/a-a-o2-gradient

Changelog

Version: 0.1.0-draft
Last code update: 2026-01-19

0.1.0-draft · 2026-01-19

Initial audit spec draft generated from HTML extraction (review required).
Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
Confirm sources are authoritative and relevant to the calculator methodology.

Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn