Respiratory Quotient (RQ) Calculator

The Respiratory Quotient (RQ) is a ratio that reveals which fuel source — carbohydrates, fats, or proteins — your body is primarily burning for energy, based on the gases you exhale. Enter your CO₂ Produced and O₂ Consumed (in mL/min) to calculate your Respiratory Quotient. You'll also see the Predominant Substrate being metabolized and a Metabolic Interpretation of what your RQ value means.

mL/min

Volume of carbon dioxide exhaled per minute

mL/min

Volume of oxygen inhaled per minute

Results

Respiratory Quotient (RQ)

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Predominant Substrate

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Metabolic Interpretation

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Frequently Asked Questions

What is respiratory quotient (RQ) and why is it important?

Respiratory quotient (RQ) is the ratio of CO₂ produced to O₂ consumed during metabolism. It indicates which type of fuel (carbohydrates, fats, or proteins) your body is primarily using for energy and helps assess metabolic efficiency.

What do different RQ values mean?

RQ values typically range from 0.7 to 1.0. An RQ of 0.7 indicates fat oxidation, 0.85 indicates protein metabolism, and 1.0 indicates carbohydrate oxidation. Values above 1.0 may suggest anaerobic metabolism or hyperventilation.

How do I measure CO₂ production and O₂ consumption?

These values are typically measured using indirect calorimetry equipment in clinical or research settings. The equipment analyzes expired air to determine gas exchange rates, usually expressed in mL/min or L/min.

What factors can affect respiratory quotient values?

RQ values can be influenced by diet composition, exercise intensity, metabolic state (fed vs fasted), disease conditions, and measurement timing. Physical activity and recent food intake significantly impact RQ measurements.

Is there a normal range for respiratory quotient?

Normal resting RQ values typically range from 0.7 to 1.0, with an average around 0.8-0.85 for mixed substrate utilization. Values outside this range may indicate specific metabolic states or measurement errors.

Can RQ help determine caloric expenditure?

Yes, RQ is used in indirect calorimetry to calculate energy expenditure more accurately. Different substrates require different amounts of oxygen and produce different amounts of CO₂ per calorie burned.

What does an RQ above 1.0 indicate?

RQ values above 1.0 may indicate anaerobic metabolism, hyperventilation, or conversion of carbohydrates to fat (lipogenesis). In clinical settings, this could suggest respiratory distress or metabolic dysfunction.