Vital capacity
A 30-year-old man who is 175 cm tall has a predicted vital capacity of 4.24725 litres by the Baldwin, Cournand and Richards equations. Enter height, age and sex to get the reference volume a healthy adult is expected to breathe out. Free in your browser.
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- Runs in your browser
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- Your data stays on your device
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Worked example
- Height
- 175
- Age
- 30
- Sex
- Male
- Predicted vc l
- 4.24725 L
- Height (cm)
- 175
- Age (years)
- 30
- Equation
- baldwin_cournand_richards
Vital capacity is the largest volume of air a person can exhale after a full inhalation. Predicted vital capacity is the reference value expected for a healthy adult of a given standing height, chronological age, and biological sex. This calculator applies the Baldwin, Cournand, and Richards equations, the classic linear reference formulas used in physiology teaching to estimate that volume in liters. Enter height in centimeters, age in years, and sex; the solver returns the predicted capacity together with the formula that produced it. Height and age must be finite positive numbers. Results are educational estimates, not a clinical diagnosis or a substitute for laboratory spirometry performed by a qualified professional.
What predicted vital capacity is and how the Baldwin equations work
Predicted vital capacity is the reference lung volume a healthy person of a stated height, age, and sex is expected to move between a complete inhalation and a complete exhalation. Vital capacity itself is the sum of tidal volume, inspiratory reserve volume, and expiratory reserve volume; the predicted figure is not a measured spirogram but a linear estimate from published reference equations so that a later measured volume can be discussed as a percent of predicted in teaching notes.
This calculator uses the Baldwin, Cournand, and Richards equations, the classic adult formulas that remain standard in physiology courses and many bedside reference cards. For males the predicted capacity in milliliters is twenty-seven point sixty-three minus zero point one one two times age in years, all multiplied by standing height in centimeters; dividing by one thousand converts the product to liters. For females the intercept is twenty-one point seventy-eight and the age coefficient is zero point one zero one, with the same height product and the same conversion to liters.
Taller stature increases predicted volume because the thoracic cage and conducting airways scale with height. Advancing age decreases predicted volume because elastic recoil and respiratory muscle strength decline on average in reference cohorts. Sex enters as two distinct coefficient sets rather than as a multiplier applied after a unisex line.
The arithmetic is closed form: a handful of multiplies and a subtraction, no lookup tables, no spline interpolation, no network call, and no dependence on the current calendar date. Treat every output as an educational reference estimate. It is not a diagnosis, not a percent-of-predicted interpretation of a real forced vital capacity maneuver, and not a substitute for a pulmonary-function laboratory or a qualified clinician.
Where a predicted vital capacity calculator earns its keep
Physiology and respiratory-therapy courses routinely ask learners to compute predicted vital capacity from height, age, and sex so they can compare a textbook spirometry vignette against a published reference without flipping sign errors in the Baldwin coefficients. Exam-prep generators need a deterministic oracle that rejects a zero or negative height instead of silently emitting a negative volume that a buggy grader might treat as success.
Product teams building educational pulmonary dashboards want a documented height-age-sex path that clients can audit by hand rather than a black-box neural estimate that mixes ethnicity, smoking history, and device brand without disclosure. Simulation labs preparing synthetic lung-function datasets need stable liter labels from known anthropometrics without network calls or model drift. Chart-review practice sometimes needs a fast offline source of predicted liters so percent-of-predicted exercises can be checked without inventing coefficients under time pressure.
Always present results as educational estimates from the published Baldwin equations; clinical interpretation of a real forced vital capacity requires calibrated equipment, published interpretation standards, and a qualified professional this tool does not replace.
What you can do with it
Physiology homework and respiratory-therapy drills
Compute predicted vital capacity from textbook height, age, and sex so learners can check Baldwin liters before grading or chart practice.
Education and simulation dashboards
Normalize user-entered stature, age, and sex into predicted vital capacity in liters for tutors, quizzes, and simple lung-volume teaching charts.
FAQ
What does the vital capacity calculator cost?
It is free in your browser on this page.
How is predicted vital capacity calculated?
The Baldwin-Cournand-Richards equations estimate VC in liters from height in centimeters, age in years, and sex. Example: 175 cm, 30 years, male yields 4.24725 L.
What happens if height or age is zero or negative?
Height and age must be positive numbers because the reference equations are undefined for non-positive stature or age.
Is predicted vital capacity a clinical diagnosis?
No. The result is an educational reference estimate from published equations. It does not interpret a measured spirogram, compute percent of predicted from a real FVC, or replace a pulmonary-function laboratory.
Why does predicted vital capacity go down with age?
Because elastic recoil and breathing-muscle strength decline on average in the reference groups. For men, each year of age takes 0.112 off the 27.63 starting value before it is multiplied by height; for women it takes 0.101 off 21.78.
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/vital-capacity \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"height":175,"age":30,"sex":"male"}'const res = await fetch("https://api.kit.forhosting.com/health/vital-capacity", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"height": 175,
"age": 30,
"sex": "male"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/health/vital-capacity",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"height": 175,
"age": 30,
"sex": "male"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/health/vital-capacity", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"height":175,"age":30,"sex":"male"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"height":175,"age":30,"sex":"male"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/health/vital-capacity", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"height": 175,
"age": 30,
"sex": "male"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "health.vital_capacity",
"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.
Limits
max_height_cm | 250 |
max_age_years | 120 |
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
Successful API calls cost $0.002 per item; failed validation is not charged.
Input contract, units, response shape, and error behaviour
Send three required fields. A one hundred seventy-five centimeter thirty-year-old male yields four point two four seven two five liters because twenty-seven point sixty-three minus zero point one one two times thirty equals twenty-four point two seven, times one hundred seventy-five, divided by one thousand. A one hundred sixty-five centimeter forty-year-old female yields two point nine two seven one liters by the female intercept and age coefficient. Optional fields that do not apply are omitted rather than returned as null. The field height is standing height in centimeters and must be a finite number strictly greater than zero and at most two hundred fifty; aliases height_cm and cm are accepted so spreadsheets and typed forms can reuse the same contract. The field age is chronological age in years and must be a finite number strictly greater than zero and at most one hundred twenty; aliases years and age_years are accepted. Zero, negative, missing, blank, non-numeric, NaN, and infinite values for height or age fail with invalid_input, because a non-positive stature or age is outside every published adult reference equation and would not describe a physical person. The field sex is biological sex for the Baldwin coefficient set and must be male or female; the aliases m, man, f, woman, and gender are accepted and normalized. On success the response echoes cleaned height_cm, age_years, and sex, returns predicted_vc_l as the capacity in liters rounded to six decimal places, tags unit as L, names equation baldwin_cournand_richards, and restates the sex-specific formula so a reviewer can recompute the product by hand. Pricing for successful API calls is the published base of $0.002 per item; validation failures do not consume prepaid balance.
Where a predicted vital capacity calculator earns its keep
On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split — free interactive exploration and a priced, identical API — matches the rest of the KIT tier-A catalog and lets you move from a classroom demo to an automated pipeline without changing the mathematical result.
Integration use cases
Deterministic test fixtures for pulmonary UIs
Generate reproducible liter predictions and formula strings for unit tests, property checks, and CI assertions on educational spirometry screens.
Technical questions
Which units does the calculator use?
Height is standing centimeters, age is years, and predicted vital capacity is returned in liters under predicted_vc_l with unit L. Convert inches to centimeters before sending height.