—
Pediatric Anesthesia Calculator
Enter the child's age and weight to get airway sizes, normal values, maintenance fluids and selected induction and resuscitation doses. If the child cannot be weighed, estimate the weight from age with the APLS formula. Each value's source is listed under Formulas & sources; resuscitation doses follow Resuscitation Council UK (2025). Check local paediatric guidance before use.
No matching items.
Patient
Body size and the weights used for drug dosing.
Physiology & fluids
Normal values, ventilation and fluid requirements.
Airway
Tube, supraglottic airway and laryngoscope sizes.
Induction
Hypnotics, sedatives and opioids. Titrate to effect.
Neuromuscular block
Relaxants and reversal.
Analgesia
Opioid, simple and adjuvant analgesics.
Antiemetics & adjuncts
PONV prophylaxis, anticholinergics and antibiotic prophylaxis.
Emergency
Resuscitation and crisis drugs (RCUK 2025, Association of Anaesthetists).
Worked example
What this calculator shows for a typical patient. Change the values above for yours.
| APLS weight for age | 16 kg |
|---|---|
| ETT, cuffed / uncuffed | 4.5 / 5.0 mm ID |
| ETT length, oral | 14 cm at lips |
| LMA Classic | 2 size |
| Maintenance fluid (4-2-1, hourly) | 52 mL/h |
| Maintenance per 24 hours | 1300 mL |
| Adrenaline, cardiac arrest | 160 µg |
| Defibrillation, first shocks (VF / pulseless VT) | 64 J |
| Refractory VF / pVT, from the 5th shock | 128 J |
Frequently asked questions
How far should an endotracheal tube be inserted in a child?
From 1 year, the oral length at the lips is about age/2 + 12 cm and the nasal length about age/2 + 15 cm. In neonates, use weight (kg) + 6 cm at the lips. These are starting estimates: confirm placement with continuous waveform capnography and clinical assessment, recheck after moving the head or tube, and get a chest X-ray if the position is uncertain.
What is the adrenaline dose in paediatric cardiac arrest?
During cardiac arrest: 10 micrograms/kg IV or IO (0.1 mL/kg of 1:10,000), up to 1 mg, repeated every 3 to 5 minutes. In non-shockable rhythms give it as soon as possible; in VF or pulseless VT give it after the third shock (Resuscitation Council UK 2025).
What size LMA does a child need?
LMA Classic sizes go by weight: under 5 kg size 1, 5 to 10 kg size 1.5, 10 to 20 kg size 2, 20 to 30 kg size 2.5 and 30 to 50 kg size 3.
What is the IV paracetamol dose for a child?
10 kg or less: 7.5 mg/kg, up to 30 mg/kg a day. Over 10 kg to 50 kg: 15 mg/kg, up to 60 mg/kg a day, and no more than 2 g a day up to 33 kg or 3 g a day up to 50 kg. Leave at least 4 hours between doses, give no more than 4 doses in 24 hours and count paracetamol from all routes. The bands follow the product licence (SmPC) for term neonates and older children; preterm neonates need specialist dosing.
Formulas & sources
How each value is calculated. Tap next to an item to jump here.
Patient
Estimated weight for age
Back to dose ↑APLS: 0–12 months (0.5 × age in months) + 4; 1–5 years (2 × age) + 8; 6–12 years (3 × age) + 7.
Use it only when the child cannot be weighed.
Related terms: APLS weight formula, paediatric weight
Physiology & fluids
Heart rate
Back to dose ↑APLS normal ranges by age.
Related terms: HR, pulse, normal values
Respiratory rate
Back to dose ↑APLS normal ranges by age.
Related terms: RR, breathing rate
Systolic blood pressure
Back to dose ↑APLS normal ranges by age. Lower limit (5th centile): 60 mmHg in neonates, 70 mmHg in infants, 70 + 2 × age (years) from 1 to 10 years, and 90 mmHg from 10 years.
Related terms: SBP, hypotension
Maintenance fluid
Back to dose ↑Adults: NICE CG174 routine maintenance, 25–30 mL/kg/day, shown per hour. The 4-2-1 rate is shown only for comparison. In obese adults use ideal body weight and the lower end: patients rarely need more than 3 L/day, and seek expert advice if the BMI is over 40 (NICE CG174 1.4.2).
Children: Holliday–Segar 4-2-1 hourly rate (4 mL/kg/h for the first 10 kg, 2 mL/kg/h for the next 10 kg, then 1 mL/kg/h), and the daily volume of 100, 50 and 20 mL/kg/day for the same bands (NICE NG29). Use isotonic fluids and reassess fluid balance and electrolytes.
These are starting points for routine maintenance, not resuscitation or replacement of losses.
Related terms: 4-2-1 rule, Holliday Segar, fluids
Airway
Endotracheal tube size
Back to dose ↑- Neonates (uncuffed, by weight): under 1 kg 2.5, 1–2 kg 3.0, 2 kg and over 3.5.
- Infants: cuffed 3.0, uncuffed 3.5.
- 1–12 years: cuffed age/4 + 3.5, uncuffed age/4 + 4, both rounded to 0.5 mm.
- Adults: female 7.0–8.0, male 8.0–9.0.
Always have a tube a size above and below ready.
Related terms: ETT, ET tube, intubation
Endotracheal tube length
Back to dose ↑- Neonates: weight (kg) + 6 cm at the lips (Tochen).
- 1–12 years: oral age/2 + 12 cm, nasal age/2 + 15 cm.
- Adults: female 19–21 cm, male 21–23 cm at the lips.
Confirm with capnography, auscultation and, if needed, a chest X-ray.
Related terms: ETT depth, insertion length
Suction catheter
Back to dose ↑Catheter size (FG) at most 2 × the tube internal diameter (mm), rounded down to an available size.
Related terms: FG, French gauge
LMA Classic
Back to dose ↑By weight (manufacturer): under 5 kg size 1, 5–10 kg 1.5, 10–20 kg 2, 20–30 kg 2.5, 30–50 kg 3, 50–70 kg 4, 70–100 kg 5, over 100 kg 6, using ideal weight when BMI is 30 or more. The row shows the maximum cuff volume. Inflate only to a cuff pressure of 60 cmH₂O.
Related terms: laryngeal mask airway, supraglottic airway, SGA
i-gel
Back to dose ↑By weight (manufacturer): 2–5 kg size 1, 5–12 kg 1.5, 10–25 kg 2, 25–35 kg 2.5, 30–60 kg 3, 50–90 kg 4, over 90 kg 5 (ideal weight when BMI is 30 or more).
Related terms: supraglottic airway, SGA
Macintosh blade
Back to dose ↑Typical sizes: neonate 0, infant to 2 years 1, 2–12 years 2, adult female 3, adult male 3–4.
Related terms: laryngoscope, Mac
Miller blade
Back to dose ↑Typical sizes: neonate 0, infant 0–1, 1–6 years 1, 6–12 years 2, adult 2–3. Straight blades suit neonates and infants.
Related terms: straight blade, laryngoscope
Nasopharyngeal airway
Back to dose ↑Children: diameter about the size of the uncuffed tube for their age. Adults: female 6.0, male 7.0. Length: from the nostril to the tragus of the ear.
Related terms: NPA, nasal airway
Induction
Propofol
Back to dose ↑Adults 1.5–2.5 mg/kg. Children (1 month–16 years) 2.5–4 mg/kg (BNF/BNFc). Give less in the elderly, in ASA 3–4 and after premedication.
Obesity: induction on lean body weight.
Related terms: Diprivan
Fentanyl
Back to dose ↑1–3 µg/kg at induction. Higher doses are used to obtund the pressor response and in cardiac anaesthesia. Obesity: lean body weight.
Related terms: Sublimaze
Neuromuscular block
Suxamethonium
Back to dose ↑Infants 2 mg/kg, children 1–2 mg/kg, adults 1–1.5 mg/kg. IM in children (no IV access): 4 mg/kg, maximum 150 mg.
Obesity: total body weight, because plasma cholinesterase activity is increased.
Avoid with hyperkalaemia, burns or crush injury over 48 h old, denervation or myopathy, and a history of malignant hyperthermia.
Related terms: succinylcholine, scoline, sux
Rocuronium
Back to dose ↑Intubation 0.6 mg/kg; rapid sequence 1–1.2 mg/kg. Reversible with sugammadex. Obesity: lean body weight (Association of Anaesthetists 2015).
Related terms: Esmeron
Analgesia
Paracetamol IV
Back to dose ↑- 10 kg or less: 7.5 mg/kg, maximum 30 mg/kg/day.
- Over 10 kg to 33 kg: 15 mg/kg, maximum 60 mg/kg/day (no more than 2 g).
- Over 33 kg to 50 kg: 15 mg/kg, maximum 60 mg/kg/day (no more than 3 g).
- Over 50 kg: 1 g, maximum 4 g/day (3 g with risk factors for hepatotoxicity).
The weight band is chosen on actual weight, as in the product licence. In obesity, the per-kg doses use lean body weight.
Related terms: acetaminophen, Perfalgan
Antiemetics & adjuncts
Ondansetron
Back to dose ↑Children 0.1–0.15 mg/kg (maximum 4 mg). Adults 4 mg (up to 8 mg). It prolongs the QT interval.
Related terms: Zofran, antiemetic, PONV
Dexamethasone
Back to dose ↑Children 0.15 mg/kg (maximum 6.6 mg). Adults 3.3–6.6 mg at induction. Inject slowly in awake patients (perineal discomfort).
Related terms: steroid, antiemetic, PONV
Atropine
Back to dose ↑Children 20 µg/kg (maximum 600 µg). Adults 300–600 µg.
Related terms: anticholinergic, vagolytic
Emergency
Adrenaline, cardiac arrest
Back to dose ↑Children 10 µg/kg (0.1 mL/kg of 1:10,000), maximum 1 mg. Adults 1 mg. Repeat every 3–5 minutes.
Related terms: epinephrine, CPR, resuscitation
Amiodarone
Back to dose ↑Shockable arrest: children 5 mg/kg (maximum 300 mg) after the 3rd and 5th shocks. Adults 300 mg after the 3rd shock, then 150 mg after the 5th.
Related terms: Cordarone, VF, pulseless VT
Defibrillation
Back to dose ↑Children: 4 J/kg for the first shocks, not above the device's adult first-shock energy (120–200 J). For refractory VF/pVT, from the 5th shock, increase stepwise up to 8 J/kg (maximum 360 J).
Adults: biphasic first shock at least 150 J (130–150 J for pulsed biphasic). Increase the energy for later shocks if the device allows (RCUK 2025).
Related terms: DC shock, VF, joules
Glucose 10%
Back to dose ↑Children 2 mL/kg of 10% (0.2 g/kg). Adults 150–200 mL of 10% over 15 minutes. Recheck glucose after 10 minutes.
Related terms: dextrose, hypoglycaemia
Main sources
- BNF and BNF for Children (NICE), current editions.
- Association of Paediatric Anaesthetists (APA) and Advanced Paediatric Life Support (APLS).
- Resuscitation Council UK, 2025 Guidelines (paediatric and adult life support) and 2021 anaphylaxis guidance.
- Association of Anaesthetists: peri-operative management of the obese surgical patient (2015), Quick Reference Handbook (local anaesthetic toxicity 3-10, malignant hyperthermia 3-8); European MH Group (2024).
- British Society for Haematology (BSH) transfusion guidelines, NICE CG174 (intravenous fluids) and product licences (SmPC, emc).
For education only. These figures support, but do not replace, clinical judgement, local protocols and the current BNF/BNFc and product literature. Check every dose before giving it and titrate to effect. See also the disclaimer.