Neonatal intubation: size and length

Disclaimer:  I have checked the formulas below, but cannot guarantee the below is up to date, or error free - please consult official sources for actual patient care! 
 
Internal Diameter

• Usually require tube internal diameter 3-3.5mm
• pre-term infants may need one of diameter 2.5 mm
• Rule of thumb: internal diameter = gestational age/10 

Tube Length

• ET Tube length = 6 + weight
• not accurate if weight < 1 kilo
  

[Source: APLS 4th ed, senior advice]