Stroke volume calculator
Subtract end-systolic from end-diastolic volume to get the blood pumped out in one beat: 120 mL minus 50 mL is a stroke volume of 70 mL, shown with its ejection fraction. Built for physiology labs and echo worksheets. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- End diastolic volume
- 120
- End systolic volume
- 50
- Stroke volume
- 70 mL
- Ejection fraction percent
- 58.3333333333
This stroke volume calculator takes end-diastolic and end-systolic ventricular volumes in milliliters and returns the volume of blood ejected in one beat. Stroke volume is defined as end-diastolic volume minus end-systolic volume: a classic one hundred twenty milliliter diastolic chamber with a fifty milliliter residual systolic chamber yields seventy milliliters, while one hundred fifty and sixty yield ninety. Those differences appear in physiology labs, echocardiography worksheets, and nursing quizzes because cardiac output is later stroke volume times heart rate. The engine is fully deterministic: the same pair of volumes always yields the same rounded result, with no network calls, no sampling, and no date-dependent shortcuts.
How end-diastolic and end-systolic volumes are read and how results stay reproducible
Optional leading plus signs and scientific notation on volume strings are allowed when they parse as finite decimals; embedded spaces around a number are trimmed, while hex prefixes and non-numeric tokens are rejected with a clear message so a bad cell does not become a wrong difference. Both values must fall between zero and ten thousand milliliters inclusive, which covers realistic human ventricular volumes from echo and MRI while blocking nonsense magnitudes.
Equal volumes yield a stroke volume of zero, which is unusual clinically but mathematically consistent and useful for edge-case tests. Negative volumes are rejected by name because a ventricle cannot hold a negative milliliter count. When EDV is positive, ejection fraction percent is the same rounded ratio of stroke volume to end-diastolic volume times one hundred; when EDV is zero that optional field is omitted rather than returned as null.
Where stroke volume fits in study, teaching, and software
Students meet stroke volume when cardiovascular labs ask for the difference between end-diastolic and end-systolic volumes, when a worksheet contrasts a seventy milliliter ejection with a smaller residual, or when a nursing quiz expects both the milliliter result and a sense of ejection fraction. Teachers can pre-generate answer keys for modest echo pairs without trusting opaque apps that silently swap units or drop the inequality check between systolic residual and diastolic fill.
Developers call the same contract from scripts to seed deterministic test vectors for cardiac UIs, to normalize user-entered milliliter pairs before charting demos, or to satisfy programming-challenge statements that demand stroke volume rather than a hand-waved interpretation. Education and simulation products use the difference when a learner types two chamber volumes and the UI must show the ejected milliliters plus a clear ejection-fraction companion without implying a medical diagnosis. Chart-review practice sometimes needs a fast offline source of differences so solutions can be checked without inventing thresholds under time pressure.
What you can do with it
Homework and physiology labs
Compute stroke volume from textbook EDV and ESV pairs and check the milliliter difference plus ejection fraction before grading or chart practice.
Education and echocardiography UIs
Normalize user-entered end-diastolic and end-systolic volumes into stroke volume for tutors, quizzes, and simple cardiac charts.
FAQ
What does the stroke volume calculator cost?
It is free in your browser on this page.
How is stroke volume calculated?
Stroke volume equals end-diastolic volume minus end-systolic volume, both in milliliters. Example: EDV 120 mL and ESV 50 mL yields 70 mL.
What happens if end-systolic volume exceeds end-diastolic volume?
End-systolic volume must not exceed end-diastolic volume because stroke volume is defined as EDV minus ESV.
Are negative ventricular volumes allowed?
Volumes must be zero or greater, and they must stay within the documented milliliter range.
Is this medical advice?
No. The tool only subtracts two milliliter volumes and, when EDV is positive, reports a companion ejection fraction. It does not diagnose conditions or replace clinical care.
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/stroke-volume \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"end_diastolic_volume":120,"end_systolic_volume":50}'const res = await fetch("https://api.kit.forhosting.com/health/stroke-volume", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"end_diastolic_volume": 120,
"end_systolic_volume": 50
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/health/stroke-volume",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"end_diastolic_volume": 120,
"end_systolic_volume": 50
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/health/stroke-volume", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"end_diastolic_volume":120,"end_systolic_volume":50}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"end_diastolic_volume":120,"end_systolic_volume":50}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/health/stroke-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
{
"end_diastolic_volume": 120,
"end_systolic_volume": 50
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "health.stroke_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.
Limits
min_ml | 0 |
max_ml | 10000 |
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
What stroke volume means and what the response contains
Stroke volume is the volume of blood ejected by a ventricle in a single beat, expressed in milliliters. End-diastolic volume is the chamber fill at the end of filling, just before ejection; end-systolic volume is the residual volume that remains after contraction. Subtracting end-systolic volume from end-diastolic volume isolates how much blood left the chamber on that beat, independent of heart rate. Cardiac output later multiplies this stroke volume by rate, but this calculator stops at the per-beat milliliter difference so physiology labs, echocardiography worksheets, and nursing quizzes can check the subtraction without mixing in pulse. The response echoes the validated end-diastolic and end-systolic volumes, returns stroke_volume in milliliters, tags unit as mL, restates the formula SV equals EDV minus ESV, and names the method edv_minus_esv. When end-diastolic volume is greater than zero the payload also includes ejection_fraction_percent, which is stroke volume divided by end-diastolic volume times one hundred, a companion teaching figure that many textbooks print next to stroke volume. There is no wearable sync path and no random noise: the engine either builds a finite non-negative difference inside the supported milliliter range or rejects the input with invalid_input. Rejected cases include missing volumes, non-finite values, negative volumes, and any case where end-systolic volume exceeds end-diastolic volume, because a negative stroke volume is not a valid ejection geometry.
How end-diastolic and end-systolic volumes are read and how results stay reproducible
The preferred fields are end_diastolic_volume for the filled chamber and end_systolic_volume for the residual chamber, both in milliliters, but aliases edv, end_diastolic, and diastolic_volume for the first field and esv, end_systolic, and systolic_volume for the second are accepted so spreadsheets, query strings, and typed forms can reuse the same contract. End-systolic volume must not exceed end-diastolic volume: when the residual chamber is larger than the filled chamber, the request fails with invalid_input explaining that stroke volume is EDV minus ESV. Pair the free browser run on this page with the priced API when you need the identical mathematical result inside an automated pipeline without re-implementing the subtraction and labels yourself.
Where stroke volume fits in study, teaching, and software
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. Pair it with other health endpoints when you are building a small lab of free, deterministic physiology helpers, and always treat the milliliter figure and ejection-fraction companion as educational summaries rather than clinical advice or treatment decisions.
Integration use cases
Deterministic test fixtures
Generate reproducible milliliter differences and ejection-fraction tags for unit tests, property checks, and CI assertions.