Flat Iron vs Sirloin Tip — What's the Difference?
Quick Answer
Flat Iron (flat iron steak) and Sirloin Tip (sirloin tip (knuckle)) are not the same cut: Flat Iron is chuck primal (Infraspinatus muscle, top blade of the shoulder clod); Sirloin Tip is round primal (Front of the rear leg, between sirloin and round).
Canonical entities: Flat Iron · Sirloin Tip
Side-by-side
| flat iron | sirloin tip | |
|---|---|---|
| Primal | chuck | round |
| Muscle / location | Infraspinatus muscle, top blade of the shoulder clod | Front of the rear leg, between sirloin and round |
| 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. | Also called the knuckle. A lean, moderately tender cut from the front of the round, near the sirloin. Used for roasts, kabobs, and stir-fry. Not from the sirloin despite the name. |
Key differences
- Different primals: chuck vs round.
- 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 Tip
Pick Sirloin Tip when its primal/muscle traits fit the dish: Also called the knuckle. A lean, moderately tender cut from the front of the round, near the sirloin. Used for roasts, kabobs, and stir-fry. Not from the sirloin despite the name.
Flat Iron and Sirloin Tip are different canonical muscles/primals: Flat Iron is chuck (Infraspinatus muscle, top blade of the shoulder clod); Sirloin Tip is round (Front of the rear leg, between sirloin and round).
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 tip (what-is) · flat iron hub · sirloin tip hub