Lumbar Puncture Depth: Research Estimates
Research-based statistical estimates only; they cannot determine an individual safe insertion depth or stopping position and do not replace individual clinical judgment.
Results update as you type. Use Enter to move to the next field.Select the next field to continue.
Research estimates by cohort
CT-derived statistical estimate; not independently validated as an adult-only method.
Outside recorded Abe cohort bounds (height 48–181.5 cm; weight 3–127.3 kg; BMI 11.7–49.7); Abe estimate withheld.
Regression from pediatric observations; no individual prediction interval is established.
Observational range only, not a calculation, prediction interval, or procedural safety boundary.
Was this calculator easy to use?
Your response is saved to improve this site. Calculator inputs and results are not sent.
Thank you! You can recommend this calculator with the share button above.
Statistical equations, cohort limits, and sources
Abe 2005 (mixed ages)
CT-derived estimate (cm) = 1 + 17 × weight (kg)/height (cm). Patients from 25 days to 80 years; reported BMI 11.7–49.7. Study R² 0.81 is not an individual uncertainty interval.
Bilić 2003 (pediatric)
Observed regression (cm) = 1.3 + 0.07 × weight (kg), with 195 children. Original publication describes children older than 3 months, but exact 3-month boundary and individual prediction intervals are not established.
Observed infant subgroup
Among infants younger than three months, many observations were between 1.0 and 1.5 cm. This is NOT a predictive model or safe stopping depth.
Hypothetical arithmetic
At 170 cm/65 kg, Abe estimate approximately 7.5 cm; at 120 cm/25 kg, Bilić estimate 3.05 cm (displayed 3.1). The model populations cannot be compared to select a clinical procedure.
Limitations
No age entry or automated method selection, puncture site, insertion angle, needle selection, safe depth, or stopping point is provided. Original source check 2026-11-10.