Tidal volume calculator
A man 170 cm tall has a predicted body weight of 66 kg, so the lung-protective 6 mL per kilogram gives about 396 mL per breath. Only sex and height count, never the scale. For learning, free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Sex
- Male
- Height
- 170
- Height (cm)
- 170 mL
- Predicted body weight kg
- 66.016
- Ml per kg
- 6
- Tidal volume ml
- 396.096
Tidal volume is the milliliter amount of air delivered with each mechanical breath, and lung-protective practice sets that amount from predicted body weight rather than from the number on the scale. This calculator takes patient sex and standing height in centimeters, applies the ARDSNet predicted-body-weight equations, multiplies by six milliliters per kilogram by default (or a positive milliliters-per-kilogram value you supply), and returns the volume in milliliters together with the predicted body weight used. Height must be a finite positive number; zero, negative, missing, or non-numeric height fails with invalid input and is not billed.
How predicted body weight sets an appropriate tidal volume
Mechanical ventilation delivers a tidal volume with every breath, and that volume is conventionally expressed in milliliters per kilogram. Using the patient's measured scale weight would overshoot in obesity and undershoot in wasting, because extra adipose tissue does not enlarge the lungs in proportion to the extra kilograms. Predicted body weight, as published by the ARDS Network, estimates a lean stature-based mass from sex and standing height so the milliliters-per-kilogram target tracks lung size rather than total mass.
The male equation is fifty plus zero point nine one times height in centimeters minus one hundred fifty-two point four. The female equation uses the same slope and reference stature with an intercept of forty-five point five kilograms. Six milliliters per kilogram of that predicted mass is the lung-protective default from the ARDSNet tidal-volume trial; four to eight milliliters per kilogram is the usual operating band.
This capability applies those closed-form equations exactly: it does not look up tables, does not call a model, and does not mix respiratory rate, positive end-expiratory pressure, or inspired oxygen into the result. Height must be a finite number strictly greater than zero in centimeters; a zero or negative height cannot represent a standing stature for this model and fails with invalid input rather than inventing an absolute-value workaround.
Predicted body weight that would not be positive, for example an extremely short stature relative to the one-hundred-fifty-two-point-four-centimeter reference, is also rejected so the milliliter output never goes non-positive. Always frame outputs as educational volumes from the published predicted-body-weight definition, not as a prescription or a substitute for a qualified clinician and a local ventilation protocol.
Where a tidal volume calculator shows up in real work
Respiratory-therapy and critical-care courses use a tidal volume calculator so students can check milliliter targets from sex and height against the ARDSNet predicted-body-weight worksheet without flipping intercepts by hand. Simulation centers and manikin labs need a deterministic oracle that returns the same milliliters for the same stature every time a scenario is reset, rather than a spreadsheet cell that drifted when someone edited the default milliliters per kilogram.
Product teams building educational ventilation widgets want a documented predicted-body-weight step that clients can audit on paper, not a black-box score that mixes driving pressure, compliance, and oxygen into one unexplained number. Research assistants preparing synthetic ICU datasets need stable tidal-volume labels from known sex and height without network calls or model drift.
If you later need body surface area, basal metabolic rate, ideal body weight for drug dosing, or a full ventilator bundle with rate and PEEP, treat those as separate search intents and landings rather than overloading this tidal volume page. Always present results as educational estimates from the ARDSNet predicted-body-weight definition; clinical ventilator settings require qualified professionals, local protocols, and context this tool does not collect.
What you can do with it
Classroom ARDSNet tidal-volume answer keys
Generate milliliter targets from sex and height so instructors and auto-graders share one transparent predicted-body-weight ground truth.
Simulation lab ventilator scenarios
Reset manikin cases with the same lung-protective milliliter volume every run instead of re-typing a spreadsheet formula.
Educational ventilation widgets
Show predicted body weight and milliliters per kilogram without mixing PEEP, FiO2, or driving pressure on the same landing.
FAQ
Why not use the patient's scale weight?
Lung size tracks stature more closely than total mass. Using scale weight would overestimate tidal volume in obesity and underestimate it in wasting. Predicted body weight from sex and height avoids that bias.
What happens if height is zero, negative, or missing?
Height must be a finite positive number in centimeters; non-positive values never produce a milliliter volume.
Can I use a milliliters-per-kilogram value other than six?
Omit it to keep the lung-protective default of 6 mL per kg of predicted body weight.
What does the tidal volume calculator cost?
The browser tool is free and runs locally.
How is predicted body weight calculated?
For men it is 50 plus 0.91 times the height in centimeters minus 152.4. For women the slope and the reference height are the same, but the starting value is 45.5 kg instead of 50.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/health/tidal-volume \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"sex":"male","height":170}'const res = await fetch("https://api.kit.forhosting.com/health/tidal-volume", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"sex": "male",
"height": 170
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/health/tidal-volume",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"sex": "male",
"height": 170
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/health/tidal-volume", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"sex":"male","height":170}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"sex":"male","height":170}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/health/tidal-volume", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"sex": "male",
"height": 170
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "health.tidal_volume",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
How predicted body weight sets an appropriate tidal volume
The computation is pure floating-point arithmetic with no network calls, no random seeds, and no wall-clock timestamps, so identical sex and height always yield identical JSON.
What you send and what you get back
Send two required fields and one optional field. A typical male of one hundred seventy centimeters at six milliliters per kilogram yields a predicted body weight of about sixty-six kilograms and a tidal volume of about three hundred ninety-six milliliters. A typical female of one hundred sixty-five centimeters at the same six milliliters per kilogram yields a smaller predicted mass and a correspondingly smaller milliliter volume. If your upstream form collects height in inches, convert to centimeters before calling so the published metric coefficients apply without a hidden unit switch. The field sex selects the intercept: male, m, or man maps to the fifty-kilogram equation; female, f, or woman maps to the forty-five-point-five-kilogram equation; the alias gender is accepted. The field height is standing height in centimeters and must be a finite number strictly greater than zero; aliases height_cm and cm are accepted. The optional field ml_per_kg is milliliters per kilogram of predicted body weight and defaults to six when omitted; aliases mlkg and vt_ml_per_kg are accepted, and a supplied value must be finite, positive, and at most twenty. Missing fields, non-numeric strings, NaN, Infinity, zero height, negative height, unrecognized sex, and milliliters-per-kilogram outside the allowed range fail with invalid_input and are not charged. On success the response returns the normalized sex, cleaned height_cm, predicted_body_weight_kg from the sex-specific equation, the ml_per_kg actually used, tidal_volume_ml as milliliters per kilogram times predicted body weight, unit equal to mL, a formula string that restates the applied equation, and method ardnet_pbw. Pricing for successful API calls is the published base of $0.002 per item; validation failures do not consume prepaid balance.
Where a tidal volume calculator shows up in real work
Because this capability is a pure parse engine, API pricing is the published base of $0.002 per successful item and failed validation does not consume balance.
Technical questions
How is tidal volume calculated from sex and height?
Predicted body weight uses the ARDSNet equations: males 50 + 0.91 × (height_cm − 152.4), females 45.5 + 0.91 × (height_cm − 152.4). Tidal volume in milliliters is ml_per_kg times that mass, defaulting to 6 mL/kg.