tPA Calculator – Stroke Dosing

Calculate weight-based IV alteplase (tPA) dosing for acute ischemic stroke - total dose, bolus, and infusion rate using the standard 0.9 mg/kg protocol, plus a check against the guideline treatment window.

Quick Facts

Dosing formula
0.9 mg/kg IV, 90 mg maximum
10% given as an IV bolus over 1 minute; the remaining 90% infused over the next 60 minutes.
Treatment window
Within 4.5 hours of onset
Guideline-supported window for eligible acute ischemic stroke patients; earlier treatment is associated with better outcomes.

Your Results

Calculated
Total alteplase dose
-
0.9 mg/kg, 90 mg maximum
IV bolus
-
10% of total dose, over 1 minute
Infusion rate
-
Remaining 90%, over 60 minutes
Treatment window
-
Time since onset vs. 4.5-hour guideline

Ready

Enter the patient's weight and time since symptom onset, then calculate.

About the tPA Calculator – Stroke Dosing

This calculator applies the standard, weight-based intravenous alteplase (tPA) dosing protocol used for eligible patients with acute ischemic stroke. It converts a patient's weight into the total dose, the initial IV bolus, and the infusion rate specified by the dosing regimen, and flags whether the entered time since symptom onset falls within the guideline-supported treatment window.

The dosing formula

Total dose is calculated as 0.9 mg per kilogram of body weight, up to a maximum of 90 mg regardless of how much a patient weighs. Ten percent of that total dose is given as an intravenous bolus over one minute, and the remaining ninety percent is infused continuously over the following sixty minutes using an infusion pump.

Why the treatment window matters

IV alteplase is most effective, and safest, the sooner it is given after symptom onset. The original NINDS trial supported treatment within 3 hours; later evidence (including the ECASS III trial) extended the window to 4.5 hours for selected patients who meet additional eligibility criteria. Outside 4.5 hours, IV alteplase is generally not indicated and other options, such as mechanical thrombectomy, may apply instead.

When to consult a professional

This tool performs the standard dosing arithmetic only. It does not screen for contraindications, exclusion criteria, or imaging findings, and it is not a substitute for clinical judgment. Any decision to administer tPA must be made by the treating stroke team based on the full clinical picture, imaging, labs, and current institutional protocol.

Frequently Asked Questions

How is the tPA (alteplase) dose calculated for stroke?
The standard IV alteplase dose for acute ischemic stroke is 0.9 mg per kilogram of body weight, capped at a maximum total dose of 90 mg. Ten percent of the total dose is given as an IV bolus over one minute, and the remaining ninety percent is infused over the next sixty minutes.
What is the treatment time window for IV tPA in stroke?
IV alteplase is guideline-supported within 3 hours of symptom onset for all eligible patients, and within 3 to 4.5 hours for selected patients who meet additional eligibility criteria. Treatment is most effective when given as early as possible; outside 4.5 hours, IV alteplase is generally not used.
Why is the alteplase dose capped at 90 mg regardless of weight?
The FDA-approved dosing regimen sets a 90 mg maximum total dose because the pivotal NINDS trial that established the 0.9 mg/kg protocol capped doses at that level. A patient weighing about 100 kg or more still receives 90 mg total, not a proportionally larger dose.

Related calculators