tPA dose calculator
A 70 kg adult gets 63 mg of alteplase in total: a 6.3 mg bolus and 56.7 mg infused over 60 minutes, at 0.9 mg per kg with a 90 mg ceiling. Educational arithmetic for stroke dosing, not a prescription. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Weight
- 70
- Weight (kg)
- 70 mg
- Dose mg per kg
- 0.9
- Max total mg
- 90
- Total mg
- 63
Intravenous alteplase, also called recombinant tissue plasminogen activator or tPA, is the classic fibrinolytic used for eligible adults with acute ischemic stroke. Published stroke protocols dose it from measured body weight at 0.9 milligrams per kilogram, never exceeding ninety milligrams, then split that total into a ten-percent bolus and a sixty-minute infusion of the remainder. This calculator accepts a single positive body weight in kilograms, applies those coefficients, and returns the total milligram dose together with the bolus milligrams so worksheets, simulators, and educational dashboards share one transparent arithmetic definition.
Why stroke alteplase is 0.9 mg/kg with a 90 mg ceiling
Alteplase for acute ischemic stroke is not a one-size milligram vial. Adult stroke protocols published by major guideline groups specify 0.9 milligrams of alteplase per kilogram of measured body weight, with an absolute ceiling of ninety milligrams so a very large patient does not receive an unbounded linear dose. Ten percent of the resulting total is given as an intravenous bolus over about one minute; the remaining ninety percent is infused over sixty minutes.
Those three numbers—zero point nine milligrams per kilogram, a ninety milligram maximum, and a ten percent bolus—are the entire arithmetic of this capability. The calculator does not score NIHSS, does not check last-known-well time, and does not screen for hemorrhage, recent surgery, or anticoagulant use; those eligibility questions belong to a clinician and a local protocol. What it does is make the milligram arithmetic transparent and reproducible.
You supply body mass in kilograms; you receive total milligrams and bolus milligrams computed from the same coefficients every time. Using actual scale weight rather than ideal body weight is the convention for this indication, which is why the only required input is a positive mass. Treat every result as an educational milligram split from the published 0.9 milligram-per-kilogram definition, never as a prescription or a substitute for a qualified stroke team.
What you send and how the milligram split is returned
Provide weight as a finite number of kilograms strictly greater than zero. On success the service multiplies weight by 0.9, caps the product at ninety milligrams, then splits the capped total into a ten-percent bolus and a ninety-percent infusion remainder. A seventy kilogram adult yields 63 milligrams total, a 6.3 milligram bolus, and 56.7 milligrams infused, with capped false.
A one-hundred-twenty kilogram adult would be 108 milligrams without a ceiling, so the result is 90 milligrams total, a 9 milligram bolus, and 81 milligrams infused, with capped true. Milligram fields are rounded to four decimal places so goldens and widgets stay byte-stable across runtimes. Pair the numbers with your own infusion-pump worksheet if you need milliliters of reconstituted solution—the capability returns milligrams of alteplase, not vial counts or diluent volumes.
Where a tPA dose calculator shows up in real work
Emergency-medicine and neurology courses use a tPA dose calculator so learners can check the 0.9 milligram-per-kilogram total and the ten-percent bolus against a paper protocol without flipping a ten-percent decimal by hand. Simulation centers and stroke-code drills need a deterministic oracle that returns the same milligrams for the same kilogram mass every time a manikin scenario is reset, rather than a spreadsheet cell that drifted when someone edited the maximum.
Product teams building educational stroke widgets want a documented milligram step that clients can audit on paper, not a black-box score that mixes door-to-needle time, blood pressure, and NIHSS into one unexplained number. Research assistants preparing synthetic emergency datasets need stable alteplase labels from known weights without network calls or model drift. If you later need tenecteplase milligrams, a heparin infusion, or a full stroke-severity score, treat those as separate search intents and landings rather than overloading this tPA page.
Always present results as educational estimates from the 0.9 milligram-per-kilogram alteplase definition; clinical administration requires qualified professionals, local protocols, and eligibility context this tool does not collect. Keep requests small, pin the rounded milligrams in tests, and you get reproducible totals and boluses for homework, LMS plugins, and edge workers without standing up a pharmacy system of your own.
What you can do with it
Classroom stroke-dose answer keys
Generate the 0.9 mg/kg total and 10% bolus from a stated kilogram mass so instructors and auto-graders share one transparent alteplase ground truth.
Simulation lab stroke-code drills
Reset manikin cases with the same capped milligram split every run instead of re-typing a spreadsheet formula during a time-critical scenario.
Educational fibrinolytic widgets
Show total, bolus, and infusion milligrams from body weight without mixing NIHSS, last-known-well, or blood-pressure screens on the same landing.
FAQ
What formula does this tPA calculator use?
Total milligrams equal 0.9 times body weight in kilograms, capped at 90 mg. The bolus is 10% of that capped total; the infusion is the remaining 90% (total minus bolus).
Why is there a 90 milligram maximum?
Adult acute-ischemic-stroke alteplase protocols cap the dose at 90 mg, which is the amount a 100 kg patient would receive at 0.9 mg/kg. Heavier patients stay at 90 mg rather than scaling without bound.
What happens if weight is zero, negative, or missing?
Weight must be a finite positive number in kilograms; non-positive values never produce a milligram dose.
Does this check whether the patient is eligible for alteplase?
No. It only converts a positive kilogram mass into milligrams. NIHSS, last-known-well, imaging, bleeding risk, and local protocol decisions stay with a qualified clinician.
What does the tPA dose calculator cost?
The browser tool is free and runs locally.
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/tpa \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"weight":70}'const res = await fetch("https://api.kit.forhosting.com/health/tpa", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"weight": 70
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/health/tpa",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"weight": 70
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/health/tpa", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"weight":70}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"weight":70}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/health/tpa", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"weight": 70
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "health.tpa",
"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
Missing, non-numeric, zero, or negative weight fails with invalid_input and is not billed. The free browser tool and the API share the same library, so a classroom demo and an automated pipeline always agree. Successful API calls use prepaid KIT balance at $0.002 per item.
Why stroke alteplase is 0.9 mg/kg with a 90 mg ceiling
A zero or negative kilogram value cannot represent a living patient's mass, so the request fails instead of taking an absolute value that would hide a data-entry error. The implementation is pure floating-point arithmetic: no network lookup of a drug table, no language model, and no clock, so identical weight always yields identical JSON.
What you send and how the milligram split is returned
The canonical field name is weight; aliases weight_kg, body_weight, and mass are accepted so forms and scripts do not need a single spelling. Numeric strings are coerced; empty strings, missing fields, NaN, Infinity, zero, and negative values fail with invalid_input naming weight and are not charged. The JSON returns weight_kg as echoed, dose_mg_per_kg equal to 0.9, max_total_mg equal to 90, total_mg, bolus_mg, infusion_mg, a boolean capped that is true when the ninety milligram ceiling bound the dose, unit equal to mg, and a formula string restating the three-step identity. Convert pounds to kilograms by dividing by 2.20462 before calling if your scale is imperial; this endpoint does not switch units internally. Pricing for successful API calls is the published base of $0.002 per item; validation failures do not consume prepaid balance.
Where a tPA dose 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 prepaid balance.