# 21 gauge needle — Hypodermic needle gauge dimensions (OD, ID, wall thickness, dead volume)

For 21 gauge needle, nominal o.d. (mm) is 0.819; nominal i.d. (mm) is 0.514; wall thickness (mm) is 0.152; dead volume (ul per 25.4 mm) is 5.271 µL/25.4 mm, verified against its source on 2026-08-27.

- **Gauge number:** 21 gauge needle _(verified: appears in the quote below)_
- **Nominal O.D. (mm):** 0.819 _(verified: appears in the quote below)_
- **Nominal I.D. (mm):** 0.514 _(verified: appears in the quote below)_
- **Wall thickness (mm):** 0.152 _(verified: appears in the quote below)_
- **Dead volume (uL per 25.4 mm):** 5.271 µL/25.4 mm _(verified: appears in the quote below)_

## What the source says

> 21 gauge needle | 0.819 | 0.514 | 0.152 | 5.271 µL/25.4 mm

## Source

- https://www.hamiltoncompany.com/laboratory-products/needles-knowledge/needle-gauge-chart

Last verified: 2026-08-27. Review by: 2029-08-26.
Part of [Hypodermic needle gauge dimensions (OD, ID, wall thickness, dead volume)](https://referencesource.org/syringe-needle-gauge-dimensions/).