Flat Iron vs Top Sirloin — What's the Difference?
Quick Answer
Flat Iron (flat iron steak) and Top Sirloin (top sirloin) are not the same cut: Flat Iron is chuck primal (Infraspinatus muscle, top blade of the shoulder clod); Top Sirloin is sirloin primal (Upper hip, above the sirloin cap (coulotte) and behind the short loin).
Canonical entities: Flat Iron · Top Sirloin
Side-by-side
| flat iron | top sirloin | |
|---|---|---|
| Primal | chuck | sirloin |
| Muscle / location | Infraspinatus muscle, top blade of the shoulder clod | Upper hip, above the sirloin cap (coulotte) and behind the short loin |
| 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. | A large, lean cut from the hip section. The top sirloin butt (NAMP 184) is the main muscle group. Versatile — grilled as steaks, roasted whole, or cut into kabobs. Moderate tenderness with good beefy flavor. Not to be confused with sirloin cap (coulotte/picanha) which sits on top of it. |
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.
Top Sirloin
Pick Top Sirloin when its primal/muscle traits fit the dish: A large, lean cut from the hip section. The top sirloin butt (NAMP 184) is the main muscle group. Versatile — grilled as steaks, roasted whole, or cut into kabobs. Moderate tenderness with good beefy flavor. Not to be confused with sirloin cap (coulotte/picanha) which sits on top of it.
Flat Iron and Top Sirloin are different canonical muscles/primals: Flat Iron is chuck (Infraspinatus muscle, top blade of the shoulder clod); Top Sirloin is sirloin (Upper hip, above the sirloin cap (coulotte) and behind the short loin).
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) · top sirloin (what-is) · flat iron hub · top sirloin hub