What Is the Tidal Volume Calculator?
Tidal volume (\(V_T\)) is the amount of air moved into or out of the lungs with each breath. In mechanical ventilation, clinicians size tidal volume to a patient's ideal body weight (IBW) rather than actual weight, because lung size scales with height, not how much a person weighs. This calculator estimates IBW from height and sex using the Devine formula, then multiplies it by your chosen mL/kg target to give a recommended tidal volume in milliliters.
How to Use It
Select the patient's sex, enter height in inches, and choose a target mL/kg. Lung-protective ventilation in ARDS commonly uses 4–8 mL/kg of IBW (often 6 mL/kg), while general settings may use up to 8 mL/kg. The calculator returns both the IBW and the resulting tidal volume.
The Formula Explained
$$V_T = \text{Target (mL/kg)} \times \text{IBW}$$ $$\text{IBW} = 50.0 + 2.3 \times \left( \text{Height (in)} - 60 \right) \quad \text{(males)}$$ $$\text{IBW} = 45.5 + 2.3 \times \left( \text{Height (in)} - 60 \right) \quad \text{(females)}$$ IBW (kg) = \(50 + 2.3 \times (\text{height in inches} - 60)\) for males, or \(45.5 + 2.3 \times (\text{height in inches} - 60)\) for females. Tidal volume = target mL/kg \(\times\) IBW. Each inch above 60 (5 ft) adds 2.3 kg.
Worked Example
A male patient is 70 inches tall, ventilated at 6 mL/kg. $$\text{IBW} = 50 + 2.3 \times (70 - 60) = 50 + 23 = 73 \text{ kg}$$ $$V_T = 6 \times 73 = 438 \text{ mL}$$ IBW = \(50 + 2.3 \times (70 - 60) = 50 + 23 = 73\) kg. Tidal volume = \(6 \times 73 =\) 438 mL.
FAQ
Why use ideal body weight instead of actual weight? Lung volume correlates with height, so using actual weight in obese patients would overestimate the safe tidal volume and risk lung injury.
What mL/kg should I use? Lung-protective protocols favor 6 mL/kg of IBW; 4–8 mL/kg is the usual range. Always follow institutional protocol and clinical judgment.
Is this a medical device? No. This is an educational tool and does not replace clinical assessment or professional medical advice.
