Suture Size Chart: USP to Metric Conversion and Uses
Suture sizes are written two ways: the USP size (like 3-0) and the metric or EP size, which is the diameter in tenths of a millimetre. This chart converts between them and shows what each size is usually used for.
How do USP suture sizes convert to metric?
The metric (EP) size is the minimum diameter in tenths of a millimetre. For synthetic sutures: 6-0 is metric 0.7, 5-0 is metric 1, 4-0 is 1.5, 3-0 is 2, 2-0 is 3, 0 is 3.5, 1 is 4 and 2 is 5. The more zeros in a USP size, the finer the thread: 3-0 is about 0.20–0.25 mm across.
For synthetic sutures. Collagen (catgut) sutures are usually one metric size larger for the same USP size.
USP to metric conversion (synthetic absorbable and non-absorbable sutures)
| USP size | Metric (EP) | Diameter (mm) | Typical use |
|---|---|---|---|
| 11-0 | 0.1 | 0.010–0.019 | Ophthalmic microsurgery |
| 10-0 | 0.2 | 0.020–0.029 | Ophthalmic and microvascular surgery |
| 9-0 | 0.3 | 0.030–0.039 | Microsurgery, nerve repair |
| 8-0 | 0.4 | 0.040–0.049 | Ophthalmic, fine vascular |
| 7-0 | 0.5 | 0.050–0.069 | Vascular, facial plastic surgery |
| 6-0 | 0.7 | 0.070–0.099 | Facial skin, small vessels |
| 5-0 | 1 | 0.100–0.149 | Face and neck skin, paediatric skin |
| 4-0 | 1.5 | 0.150–0.199 | Skin of hands and limbs, subcuticular |
| 3-0 | 2 | 0.200–0.249 | Skin of trunk and scalp, subcutaneous tissue |
| 2-0 | 3 | 0.300–0.339 | Subcutaneous tissue, fascia, ligation |
| 0 | 3.5 | 0.350–0.399 | Fascia, muscle, drains |
| 1 | 4 | 0.400–0.499 | Abdominal wall closure, fascia |
| 2 | 5 | 0.500–0.599 | Abdominal closure, orthopaedics |
| 3 and 4 | 6 | 0.600–0.699 | Orthopaedics, tendon repair |
| 5 | 7 | 0.700–0.799 | Orthopaedics, heavy retention |
Diameters follow the USP / EP limits for synthetic sutures; collagen (catgut) sutures use different limits, usually one metric size larger for the same USP size. Typical uses are a general guide: the surgeon chooses the size.
We manufacture surgical sutures from USP 8-0 to 2, made to USP and EP, with a choice of needle types and lengths.
Frequently asked questions
What does 3-0 mean on a suture?
3-0 (also written 000) is a USP size. The more zeros, the finer the thread: 3-0 is metric size 2, about 0.20–0.25 mm in diameter, and is often used for skin on the trunk and for subcutaneous tissue.
Which is thicker, 2-0 or 4-0 suture?
2-0 is thicker. In USP sizes, a bigger number before "-0" means a finer thread, so 4-0 (metric 1.5) is finer than 2-0 (metric 3).
What is the metric (EP) size of a suture?
The metric size, used in the European Pharmacopoeia, is the minimum diameter in tenths of a millimetre: metric 2 is at least 0.20 mm across. It is printed on suture packs next to the USP size.
Do catgut sutures convert the same way?
No. Collagen sutures such as catgut have different diameter limits, so the same USP size is usually one metric size larger than for a synthetic suture. Always read the metric size on the pack.
Which suture sizes should a hospital stock?
Most general hospitals stock 1, 0, 2-0, 3-0 and 4-0 in absorbable (PGA, PGLA) and non-absorbable (nylon, polypropylene, silk) materials, with 5-0 and 6-0 for faces and children. Specialist units add the finer sizes. Order each size, material, needle and length as a separate line.
Buyer guides on this topic
- Surgical Sutures Quality Benchmark: PGA vs. Polyglactin 910 vs. Silk (Tensile Retention & Needle Sharpness)
- Surgical Sutures Manufacturer India: Absorbable (PGA, PGLA) vs Non-Absorbable (Silk, Nylon) Selection
- Polyglycolic Acid (PGA) vs Polyglactin 910 (PGLA) Braided Absorbable Sutures: Vietnam Hospital Tender Selection Criteria
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