Children's Acetaminophen Dose Calculator
Weight based children's acetaminophen dose in mg and mL with daily max.
What it does
Acetaminophen is the most common children's fever drug and the most common overdose call. The margin is wide per dose yet narrow per day: 15 mg per kg works beautifully every 4 hours, while a sixth dose or a hidden combo product pushes the liver. Weight math plus label reading prevents both failures.
The tool above computes 15 mg per kg per dose with a 1000 mg cap. Enter weight in kg or lb. It returns the mg dose, the mL of 160 mg per 5 mL liquid, and the 5 dose daily max. Defaults of 20 kg open solved at 300 mg with 9.4 mL.
The 15 sits at the top of the safe 10 to 15 range for a reason. Trials show 10 works, 15 works slightly longer, and above 15 adds liver risk without comfort gain. Five doses per day caps totals near 75 mg per kg, the standard ceiling pediatric societies quote.
Hidden acetaminophen causes most accidents. Cough syrups, prescription pain combos, and sleep aids often contain it under abbreviations like APAP. The page counts only what you enter, so audit the cabinet before the first dose and write each dose down.
Use the table for common weights, then dose the child. Measure with the syringe, space doses 4 hours apart, and stop when fever or pain resolves rather than finishing a schedule.
How to use
- Pick metric (kg) or imperial (lb).
- Enter the child's current weight.
- Read the mg dose first, then mL.
- Give every 4 hours as needed.
- Count 5 doses max per 24 hours.
- Check every label for hidden acetaminophen.
Formula
- Weight
- Body weight: kg in metric mode, lb converted inside in imperial.
- 15 mg/kg
- 15 mg per kg per dose.
- 32 mg/mL
- 160 mg per 5 mL liquid strength.
- Daily max
- Five doses maximum per 24 hours.
Children's liquid at 160 mg per 5 mL, which is 32 mg per mL. Dosing at 15 mg per kg sits inside the 10 to 15 safe and effective range, every 4 hours as needed, maximum 5 doses per 24 hours. Never combine with other acetaminophen containing products.
Worked example
Example: 20 kg child
A 20 kg child needs acetaminophen. Find the dose in mg and mL.
- Dose: 15 mg x 20 kg = 300 mg.
- Liquid: 300 / 32 = 9.4 mL of 160 mg per 5 mL.
- Interval: every 4 hours as needed.
- Daily max: 5 doses x 300 = 1500 mg.
- Count every source: no other acetaminophen products.
- Imperial mirror: 44 lb gives 299.4 mg with 9.4 mL.
Reference table
| Weight | Dose | Liquid | Daily max |
|---|---|---|---|
| 12 kg | 180 mg | 5.6 mL | 900 mg |
| 20 kg (worked) | 300 mg | 9.4 mL | 1500 mg |
| 30 kg | 450 mg | 14.1 mL | 2250 mg |
| 44 lb (imperial) | 299.4 mg | 9.4 mL | 1497 mg |
Limits
- Standard 160 mg/5 mL only; check the bottle.
- Under 24 lb or 2 years needs the doctor.
- Counts only entered doses, not hidden sources.
- Liver disease changes everything: ask first.
Common mistakes
- Giving a sixth dose in 24 hours.
- Stacking cold medicines with acetaminophen.
- Using kitchen spoons for mL.
- Dosing by age instead of weight.
- Missing the 1000 mg single cap.
Try it yourself
Quick checks. Answers sit tucked under each question.
44 lb child in imperial mode?
19.96 kg x 15 = 299.4 mg. Liquid 299.4 / 32 = 9.4 mL. Daily 5 x 299.4 = 1497 mg.
90 kg teen (cap case)?
90 x 15 = 1350, capped at 1000 mg. Liquid 1000 / 32 = 31.3 mL. Daily 5 x 1000 = 5000 mg.
Label says 5 mL for 24 to 35 lb?
The label bands 24 to 35 lb at 5 mL (160 mg). At 15 kg that is 10.7 mg per kg, inside the 10 to 15 range.
Questions
What is the standard dose?
15 mg per kg every 4 hours, within the 10 to 15 safe range, max 5 doses in 24 hours. Liver injury starts with extra doses, not single ones.
What concentration does the page assume?
160 mg per 5 mL, so 32 mg per mL. Divide the mg dose by 32 for mL. Infant drops match the same strength per mL.
What about small children?
Under 24 lb or under 2 years needs the doctor. The 5 dose and liver rules apply at every age.
Why does 44 lb match 20 kg?
19.96 kg x 15 = 299.4 mg with 9.4 mL and 1497 mg daily max. Same child, same answer.
Is there a single dose cap?
1000 mg single dose. Heavy children hit the adult cap before the weight math does; the page applies it.
What causes overdoses?
Severe liver damage from stacking cold medicines, prescription combos, and repeated doses. Read every label and count 5 max.
Sources
- DailyMed: children's acetaminophen 160 mg/5 mL label and liver warning
- AAP Pediatrics: fever and antipyretic use, 10 to 15 mg/kg