Adult: depth = 1+ 17*(weight/height)

Pediatric: depth = 1 + 10*(weight/height)

depth, height in cm
weight in kg

Note: Adult calculation was from measurements from CT's measuring to central canal. Peds calculation performed retrospectively. Estimates should thus be used to guide needle length choice, but not necessarily insertion depth.

 

Keith, KK et al. Lumbar puncture needle length determination. AJEM. 2005 Oct 23(6):742-6. Link

Chong, SY et al. Accurate prediction of needle depth required for successful lumbar puncture. AJEM. 2010 Jun 28(5):603-6. Link