Shopping for flat-back body jewelry online can feel confusing when sizing is listed in gauges (G) and millimeters (mm) rather than standard inches.
Wearing the wrong size affects both aesthetic appeal and piercing health:
- A post that is too short pinches tissue, restricts blood circulation, and risks embedding into swollen skin.
- A post that is too long snags easily on hair or clothing, tilts sideways, and triggers stubborn irritation bumps.
Quick Sizing Rule: Gauge (G) measures post thickness (smaller number = thicker bar). Length (mm) measures only the smooth wearable shaft between the base disc and top.
1. Piercing Gauge Guide (Post Thickness)
- 20G (0.8mm): Standard traditional earlobe earring thickness. Best for healed lower lobe piercings.
- 18G (1.0mm): Petite and versatile thickness. Ideal for upper lobes, healed nose piercings, and delicate cartilage studs.
- 16G (1.2mm): The universal standard for cartilage piercings (Helix, Conch, Tragus, Flat, Forward Helix) and lip piercings. Provides structural stability and prevents cheese-cutter damage.
- 14G (1.6mm): Thicker gauge used for industrial barbells, belly button (navel) rings, and nipple piercings.
2. Flat Back Post Length Guide (Wearable Length)
- 5mm (3/16"): Extra short and snug. Best for thin earlobes and shallow tragus piercings.
- 6mm (1/4"): Most popular healed size. Delivers a flush fit for standard earlobes, healed tragus, and healed helix piercings.
- 8mm (5/16"): The everyday cartilage standard. Ideal for conch, thicker lobes, nose studs, and healing stages with mild swelling.
- 10mm (3/8"): Extra long. Designed for initial piercings with fresh swelling, thick conch cartilage, or lip piercings.
3. Placement Sizing Quick Match
- Standard Lobe: 20G or 18G | 6mm or 8mm
- Helix / Flat / Forward Helix: 16G or 18G | 6mm (healed) or 8mm (standard)
- Conch: 16G | 8mm (healed) or 10mm (initial swelling / thick cartilage)
- Tragus: 16G or 18G | 6mm
- Nostril: 18G or 20G | 6mm (flat back) or standard 6.5mm L-shape/screw
- Septum / Daith (Hoop Inner Diameter): 16G | 8mm or 10mm diameter
4. How to Measure Your Piercing at Home (3 Steps)
- Use a Well-Fitting Post: Pick a flat back post that already fits comfortably flush in your piercing.
- Measure the Wearable Shaft: Lay the post flat on a ruler starting at the 0 mm mark. Measure only the smooth bar between the base disc and top connection point.
- Add Room if Swollen: If your piercing is currently irritated or healing, add 1mm to 2mm for breathing room.
Frequently Asked Questions
Can I wear an 18G post in a 16G cartilage hole?
Yes. An 18G post (1.0mm) is slightly thinner than a standard 16G post (1.2mm) and will slide in easily without resistance.
Why is my flat back earring tilting sideways?
A tilting post usually means the bar is too long for your ear thickness, allowing gravity or sleep pressure to pull it off-center. Downsizing to a 6mm post solves this.
How is flat back labret length measured?
Post length measures only the wearable smooth shaft between the flat base disc and where the top connects, excluding the base and decorative end.