Paediatric · Dosing
Pediatric Dose Calculator
Weight-based dosing for paracetamol, ibuprofen, and common paediatric antibiotics. UK BNFC / US AAP doses. Plus safety limits, overdose thresholds, common dosing errors, when to call.
Last reviewed 31 May 2026
Paediatric dose calculator
Weight-based medication dose (mg/kg)
Medication
Standard antipyretic / analgesic. Age ≥ 2 months and weight ≥ 4 kg (UK BNFc); from birth in some specialist contexts.
Units
kg
mo
Enter weight and age to calculate the dose.
Safety rules
- NEVER aspirin in under-16s with fever (Reye syndrome).
- NEVER ibuprofen under 3 months. Avoid in dehydration.
- NEVER codeine / dihydrocodeine / tramadol under 12.
- Use a dosing syringe — kitchen teaspoons are inaccurate.
- If unsure — call your GP, pharmacist, or NHS 111 / Poison Control.
Doses calibrated against the BNF for Children (BNFc 2024-2025) and AAP / Lexicomp paediatric drug references. This calculator is a CHECK, not a prescription — always verify against product label and clinician guidance.
What does this mean?
The most common cause of paediatric medication errors at home is the wrong dose for weight, usually too much. A few key safety rules: (1) use the oral syringe that comes with the bottle, not a kitchen spoon (teaspoons vary 2–7 mL); (2) check the strength (infant drops vs children’s suspension are different concentrations — dosing by mL is meaningless without the strength label); (3) respect the daily max (paracetamol 60 mg/kg/day; ibuprofen 30 mg/kg/day); (4) never aspirin in < 16 y with fever (Reye syndrome); ibuprofen NOT under 3 months and avoid in dehydration; never codeine/tramadol < 12 y; (5) if treating fever, the goal is comfort, not a target temperature (NICE NG143, AAP 2011 reaffirmed 2020) — don’t alternate antipyretics on a clock, treat symptoms.
Paracetamol dose
15 mg/kg every 4-6 hours, max 4 doses in 24h. MAX single dose 1 g. MAX daily 60 mg/kg/day or 4 g/day, whichever is lower.
- Newborn (under 2 months): 10 mg/kg under specialist guidance.
- 3 months - 5 years: infant paracetamol suspension 120 mg/5 ml.
- 6+ years: 250 mg/5 ml suspension or 500 mg tablets.
Ibuprofen dose
10 mg/kg every 6-8 hours, max 3 doses in 24h. MAX daily 30 mg/kg/day or 1.2 g/day, whichever is lower.
- 3+ months AND 5+ kg only — KEY restriction.
- AVOID in: dehydration, chickenpox / shingles, severe asthma, kidney impairment, peptic ulcer, bleeding disorders.
- CAN take with paracetamol — alternate every 3 hours if needed.
Weight-based dose tables
Paracetamol
- 5 kg: 75 mg = 3 ml of 120 mg/5ml suspension
- 10 kg: 150 mg = 6 ml
- 15 kg: 225 mg = 9 ml
- 20 kg: 300 mg = 12 ml
- 25 kg: 375 mg = 15 ml
- 30 kg: 450 mg = 18 ml
- 40 kg+: 500 mg single dose (adult)
Ibuprofen
- 5 kg (3+ months only): 50 mg = 2.5 ml of 100 mg/5ml
- 10 kg: 100 mg = 5 ml
- 15 kg: 150 mg = 7.5 ml
- 20 kg: 200 mg = 10 ml
- 25 kg: 250 mg = 12.5 ml
- 30 kg: 300 mg = 15 ml
- 40 kg+: 400 mg single dose
Common antibiotics & uses
- Amoxicillin — strep throat, otitis media, pneumonia (first-line).
- Augmentin / Co-amoxiclav — sinusitis, dental, beta-lactamase strains.
- Phenoxymethylpenicillin — strep throat, dental.
- Cephalexin / cefuroxime — skin infections, UTI.
- Flucloxacillin — skin / soft tissue.
- Clarithromycin / azithromycin — penicillin allergic; atypical pneumonia.
- Trimethoprim / nitrofurantoin — UTI.
- Metronidazole — anaerobes, dental, C. diff.
All weight-based dosing per UK BNFC / US BNF for Children.
Can I give paracetamol and ibuprofen together?
YES, alternating in some situations. NICE: not routinely; only if child distressed and one not enough. ALTERNATE every 3 hours (paracetamol-ibuprofen-paracetamol-ibuprofen). DON’T alternate routinely — increases dosing error risk. Record doses given. Treat discomfort, not the thermometer reading.
Paracetamol overdose
THERAPEUTIC max: 60 mg/kg/day or 4 g/day, whichever lower. ACCIDENTAL OVERDOSE: > 75 mg/kg in 24h.
CALL POISONS for any concern:
- UK: NPIS 0344 892 0111 or NHS 111
- US: Poison Control 1-800-222-1222
SIGNS of paracetamol overdose may not appear for 24-72 hours — DON’T wait for symptoms. Treatment with N-acetylcysteine (NAC) within 8 hours is very effective.
Common dosing errors
- WRONG STRENGTH suspension — 120 mg vs 250 mg vs 500 mg paracetamol all exist. Check label every time.
- KITCHEN SPOONS — vary wildly. Use syringe.
- DOUBLE-UP with cold-and-flu products containing same ingredient.
- Using age-band that’s conservative for child’s weight.
- Mistaking ml for mg or vice versa.
- Giving adult tablets to child.
- Crushing tablets that shouldn’t be crushed.
Brand vs generic medicines
- Calpol = paracetamol
- Nurofen = ibuprofen
- Anadin — mixed (DON’T USE in children — aspirin).
Generic versions equally effective and cheaper. CHECK active ingredient and strength. NEVER aspirin in under-16s with viral infection — Reye’s syndrome risk.
Different scenarios — common dosing situations
Scenario 1: 12-month-old, 9 kg, fever 38.5 °C, uncomfortable
Paracetamol 135 mg (~5.5 ml of 120 mg/5ml) OR ibuprofen 90 mg (~4.5 ml of 100 mg/5ml). Either fine. Treat comfort. Keep hydrated.
Scenario 2: 4-year-old, 16 kg, persistent fever 5 days, irritable
240 mg paracetamol (10 ml of 120 mg/5ml) OR 160 mg ibuprofen. PERSISTENT 5+ days = GP review for source (UTI, otitis media, Kawasaki, etc.). Don’t just keep medicating.
Scenario 3: 2-week-old newborn, fever 38 °C
DON’T medicate at home. NICE NG143: ANY fever under 3 months = same-day emergency assessment. Sepsis workup possible.
Scenario 4: Child with chickenpox, painful
PARACETAMOL only. AVOID IBUPROFEN in chickenpox (linked to severe skin / soft-tissue infections including necrotising fasciitis).
Scenario 5: Antibiotic prescribed for strep throat, parent unsure of dose
Check BNFC: amoxicillin 25-50 mg/kg/day in 3 doses for strep throat (max 1 g per dose). Pharmacist or GP can verify. Complete the FULL COURSE even if better.
Care guidance — medicating safely
- Weigh your child — weight-based dosing accurate.
- Use syringe not kitchen spoon.
- Check strength every time — brands have multiple strengths.
- Record doses — paper or app.
- Don’t double-dose with cold/flu products containing same ingredient.
- Read every label.
- Lock medications out of children’s reach.
- Don’t crush tablets not designed to crush (check with pharmacist).
- Complete full antibiotic course even when better.
- Don’t share antibiotics — resistance.
- If unsure — ask pharmacist (immediate, free, accessible).
Sources
- British National Formulary for Children (BNFC). Updated annually.
- NICE NG143. Fever in under 5s.
- AAP. Clinical Report: Acetaminophen / Ibuprofen for Children.
- NHS. Medicines for children.
- NPIS (UK National Poisons Information Service).
Recommended for this calculator
Frequently asked questions
How much paracetamol can I give my child?
STANDARD: 15 mg/kg every 4-6 hours (max 4 doses in 24h). MAX SINGLE DOSE: 1 g (15 mg/kg or 1 g, whichever is lower). MAX DAILY DOSE: 60 mg/kg/day or 4 g/day, whichever is lower. INFANT PARACETAROL (120 mg / 5 ml suspension): for 3 months to 5 years; 2.5-5 ml depending on weight. SIX PLUS YEARS: 250 mg / 5 ml suspension or 500 mg tablets. NEWBORN under 2 months: 10 mg/kg (lower dose due to immature liver metabolism); only under specialist guidance. CALCULATOR uses these standard NICE / BNF for Children doses.
How much ibuprofen can I give my child?
STANDARD: 10 mg/kg every 6-8 hours (max 3 doses in 24h). MAX DAILY DOSE: 30 mg/kg/day or 1.2 g/day, whichever is lower. INFANT IBUPROFEN (100 mg / 5 ml suspension): for 3 months PLUS WEIGHT 5+ KG (key restriction). Under 3 months / under 5 kg: NOT recommended without specialist input. AVOID in: dehydration, chickenpox / shingles (linked to severe skin infections), severe asthma, kidney impairment, peptic ulcer, bleeding disorders. CAN TAKE WITH paracetamol — alternate every 3 hours if needed (NICE).
Can I give paracetamol and ibuprofen together?
YES, alternating in some situations. NICE: not routinely; only if child distressed and one not enough. ALTERNATE every 3 hours (paracetamol-ibuprofen-paracetamol-ibuprofen). DON'T alternate routinely — increases dosing error risk. RECORD doses given (parental dosing diary helps). The goal is comfort, not chasing a number on the thermometer. Most fevers don't need treating unless child is uncomfortable.
What's the difference between paracetamol and ibuprofen for fever?
PARACETAMOL: works on fever and pain. Safer first-line. Can use from birth (with specialist input under 2 months) and 3+ months routinely. IBUPROFEN: works on fever, pain AND inflammation (anti-inflammatory). 3+ months AND 5+ kg only. Avoid in dehydration, asthma, chickenpox. ASPIRIN: NEVER for children under 16 with viral infection (Reye's syndrome risk). NICE: paracetamol or ibuprofen for distressed febrile children; not both routinely; treat the discomfort not the number.
What's the dose of paracetamol by weight?
5 kg baby: 75 mg = 3 ml of 120 mg/5ml suspension. 10 kg toddler: 150 mg = 6 ml. 15 kg child: 225 mg = 9 ml. 20 kg child: 300 mg = 12 ml. 25 kg child: 375 mg = 15 ml. 30 kg child: 450 mg = 18 ml. 40 kg+ child: 500 mg single dose (adult). Use the syringe / measuring spoon that came with the bottle for accuracy. Don't use kitchen spoons (vary in size).
What's the dose of ibuprofen by weight?
5 kg baby (3+ months only): 50 mg = 2.5 ml of 100 mg/5ml. 10 kg: 100 mg = 5 ml. 15 kg: 150 mg = 7.5 ml. 20 kg: 200 mg = 10 ml. 25 kg: 250 mg = 12.5 ml. 30 kg: 300 mg = 15 ml. 40 kg+: 400 mg single dose. Always check the strength of the suspension you have (100 mg/5 ml standard for infants; 200 mg/5 ml for older children; 400 mg tablets for school age and up).
What antibiotics work for which conditions?
Common paediatric oral antibiotics (UK BNFC): AMOXICILLIN — strep throat, otitis media, pneumonia (first-line). AUGMENTIN (amoxicillin + clavulanate) — sinusitis, dental, beta-lactamase strains. CO-AMOXICLAV — same as Augmentin. PHENOXYMETHYLPENICILLIN — strep throat, dental. CEPHALEXIN / CEFUROXIME — skin infections, UTI. FLUCLOXACILLIN — skin / soft tissue. CLARITHROMYCIN / AZITHROMYCIN — penicillin allergic; atypical pneumonia. TRIMETHOPRIM / NITROFURANTOIN — UTI. METRONIDAZOLE — anaerobes, dental, C. diff. All weight-based dosing — calculator gives BNFC standard doses.
Can I give my child Calpol / Nurofen / Anadin?
BRAND vs GENERIC: Calpol = paracetamol; Nurofen = ibuprofen; Anadin = brand mixing (aspirin + paracetamol — DON'T USE in children). Generic versions are equally effective and cheaper. CHECK ACTIVE INGREDIENT and strength on bottle. Don't double up — Calpol AND paracetamol AND any other 'cold and flu' product containing paracetamol = overdose risk. READ EVERY LABEL.
What if I gave too much paracetamol?
OVERDOSE risk varies. THERAPEUTIC max: 60 mg/kg/day or 4 g/day, whichever is lower. ACCIDENTAL OVERDOSE: > 75 mg/kg in 24h. CALL POISONS (UK NPIS 0344 892 0111 or 111; US Poison Control 1-800-222-1222) for any concern. SIGNS of paracetamol overdose may not appear for 24-72 hours — DON'T wait for symptoms. Treatment with N-acetylcysteine (NAC) within 8 hours of overdose is very effective. NEVER assume 'a bit too much' is fine. Children's liver less able to handle than adults.
Why is age vs weight dosing important?
WEIGHT-BASED dosing is more accurate because: children of same age vary hugely in weight; medication clearance correlates with weight not age; underweight / overweight children differ. AGE-BASED dosing (e.g. 'one spoonful for 2-3 years') is approximate and conservative for population. WEIGHT-BASED dosing matches BNFC / AAP standards. CALCULATOR USES WEIGHT. If you don't know weight, weigh first (kitchen scales work for under-25 kg) or use age-based as starting point and weigh next visit.
How often can I give doses?
PARACETAMOL: every 4-6 hours, max 4 doses in 24h. IBUPROFEN: every 6-8 hours, max 3 doses in 24h. ANTIBIOTICS: schedule varies — amoxicillin every 8h, augmentin every 12h, azithromycin once daily. RECORD doses on a chart / phone notes. AVOID running too late and 'catching up' with double doses. Get a steady schedule from start of illness.
What about medication during teething?
TEETHING is overrated as a symptom. Genuine teething: mild gum discomfort, drooling, hand-mouthing, mild fussiness; usually doesn't need medication. NOT TEETHING: fever ≥ 38°C; significant distress; diarrhoea; persistent illness. NICE: don't blame teething for moderate-severe symptoms. AT-HOME: cold teether toys, cold cloth, gentle gum massage. PARACETAMOL: short-term if genuinely uncomfortable; not first-line. AVOID: amber necklaces (strangulation risk); homeopathic teething tablets (some recalled by FDA for belladonna); teething gels with benzocaine (FDA contraindicated under 2; UK rare); rubbing alcohol on gums.
What are common dosing errors?
(1) WRONG STRENGTH suspension — 120 mg vs 250 mg vs 500 mg paracetamol all exist. CHECK label every time. (2) KITCHEN SPOONS — vary wildly. Use syringe. (3) DOUBLE-UP with cold-and-flu products containing same active ingredient. (4) Using age-band that's actually conservative for child's weight. (5) Mistaking 'mL' for 'mg' or vice versa. (6) Giving adult tablets to child. (7) Crushing tablets that shouldn't be crushed. RECORD doses to avoid confusion when both parents involved.
When should I call about a medication concern?
URGENT — NPIS (UK) / Poison Control (US): suspected overdose; child swallowed someone else's medication; medication error of significant amount. GP / HV: persistent fever despite right doses; symptoms not improving on appropriate treatment; suspected medication side effects. ROUTINE: questions about dosing, alternatives, interactions. PHARMACIST (often immediately accessible) for non-emergency questions about over-the-counter medication.
Are 'natural' remedies safer than medication?
NOT NECESSARILY. 'Natural' doesn't mean 'safe'. Many herbal products: untested in children; interact with prescribed medications; contain heavy metals / contaminants (especially imported); have inadequate dosing data. NICE: paracetamol / ibuprofen safer than most herbal alternatives. Exceptions where evidence supports: HONEY for cough (over 12 months only); GINGER for nausea; PROBIOTICS for some specific situations. Discuss any herbal medication with GP / pharmacist. Don't combine without checking.
How does this relate to other calculators on BumpBites?
Companion: /calculators/baby-fever for fever decision-making; /calculators/ors-rehydration for hydration; /calculators/croup-westley for dexamethasone dosing; /calculators/pews-paediatric for severity; /calculators/baby-cough for cough management; /calculators/baby-percentile for weight tracking.