Flat Iron vs Sirloin Cap — What's the Difference?
Quick Answer
Flat Iron (flat iron steak) and Sirloin Cap (sirloin cap) are not the same cut: Flat Iron is chuck primal (Infraspinatus muscle, top blade of the shoulder clod); Sirloin Cap is sirloin primal (top sirloin cap (coulotte)).
Canonical entities: Flat Iron · Sirloin Cap
Side-by-side
| flat iron | sirloin cap | |
|---|---|---|
| Primal | chuck | sirloin |
| Muscle / location | Infraspinatus muscle, top blade of the shoulder clod | top sirloin cap (coulotte) |
| Character | The second most tender muscle on the entire animal, after the tenderloin. A flat, rectangular steak extracted from the top blade by splitting it along the central connective tissue. Uniform thickness makes it ideal for grilling. Also known as butler's steak in the UK. | Triangular cap on the top sirloin; prized as picanha in Brazil. |
Key differences
- Different primals: chuck vs sirloin.
- Texture and slicing: compare fibrous, grain-heavy cuts vs more tender steak-style muscles based on each cut’s description.
- Retail naming diverges by country—always map through a canonical cut when translating menus or labels.
When to use each
Flat Iron
Pick Flat Iron when you want its specific marbling/texture profile: The second most tender muscle on the entire animal, after the tenderloin. A flat, rectangular steak extracted from the top blade by splitting it along the central connective tissue. Uniform thickness makes it ideal for grilling. Also known as butler's steak in the UK.
Sirloin Cap
Pick Sirloin Cap when its primal/muscle traits fit the dish: Triangular cap on the top sirloin; prized as picanha in Brazil.
Flat Iron and Sirloin Cap are different canonical muscles/primals: Flat Iron is chuck (Infraspinatus muscle, top blade of the shoulder clod); Sirloin Cap is sirloin (top sirloin cap (coulotte)).
Choose based on tenderness, marbling, grain direction, and how you plan to cook (sear vs braise vs slice thin).
Read the full guides: flat iron (what-is) · sirloin cap (what-is) · flat iron hub · sirloin cap hub