What Is the Tylenol (Acetaminophen) Overdose Calculator?
This educational tool estimates the ingested dose of acetaminophen (paracetamol) in milligrams per kilogram of body weight and compares it against a commonly cited toxicity threshold. Acute single-ingestion toxicity is often considered possible at roughly 150 mg/kg, with 200 mg/kg used as another reference point in some protocols. It is not a diagnostic device.
How to Use It
Enter the patient's body weight in kilograms, the number of tablets or doses taken, the strength of each tablet in milligrams, and choose the toxic threshold you want to compare against. The calculator multiplies tablets by strength to get the total milligrams ingested, then divides by weight to get the dose per kilogram.
The Formula
Ingested Dose (mg/kg) = (Number of Tablets × Strength per Tablet in mg) ÷ Body Weight in kg. If the resulting dose is greater than or equal to the chosen threshold (150 or 200 mg/kg), the result flags a potential risk.
$$\text{Dose}_{\text{mg/kg}} = \frac{\text{Tablets} \times \text{Strength (mg)}}{\text{Weight (kg)}}$$$$\text{Risk if } \text{Dose}_{\text{mg/kg}} \ge \text{Threshold}$$
Worked Example
A 70 kg adult takes twenty 500 mg tablets: total = \(20 \times 500 = 10{,}000\) mg.
$$\text{Dose} = \frac{10{,}000}{70} \approx 142.86 \text{ mg/kg}$$Against the 150 mg/kg threshold that is about 95% of the threshold and below it, so risk is flagged as 0. A 50 kg person taking thirty 500 mg tablets ingests 15,000 mg, or 300 mg/kg — well above the 200 mg/kg threshold (150% of it), flagging risk as 1.
$$\text{Dose} = \frac{30 \times 500}{50} = \frac{15{,}000}{50} = 300 \text{ mg/kg}$$FAQ
Is this a substitute for medical care? No. In any suspected overdose, contact emergency services or Poison Control immediately regardless of this estimate.
Which threshold should I use? 150 mg/kg is more conservative; some references use 200 mg/kg. Clinicians rely on serum levels and the Rumack-Matthew nomogram, not weight-based estimates alone.
Does timing matter? Yes — risk assessment depends heavily on time since ingestion and serum acetaminophen levels, which this simple calculator does not model.
