Buying guide · A method vs a muscle
London broil vs flank steak
London broil is a way of cooking beef and flank steak is a cut: the two are not the same thing, although the name first belonged to flank. In American shops a package labeled London broil is now usually top round, a lean steak from the inside of the hind leg, while flank steak is the thin belly muscle with long, coarse fibers. Both are marinated, cooked hot to medium-rare and sliced thin across the grain.
Buying guides written to the same standard as the rest of Steakpedia: tested or sourced, never ranked by payment. Some links may earn a commission, which never changes what we recommend.
| London broil (top round) | Flank steak | |
|---|---|---|
| Primal | Round (hind leg), inside | Flank |
| Muscles | Semimembranosus, adductor | Rectus abdominis |
| Weight | — | 700 g / 25 oz–1.2 kg (1.5–2.6 lb) |
| Best cooked | Marinated, broiled or grilled hot to 54 °C / 129 °F, sliced thin | Hot and fast to medium-rare, sliced thin across the grain |
| United States | Top round · inside round | Flank steak · London broil (as a preparation) |
| United Kingdom | Topside | Flank · bavette (often also the flap) |
| Argentina | Nalga de adentro · nalga | Vacío region; the flank steak proper is sold as bife de vacío. Matambre is a different muscle (cutaneous trunci, over the ribs). |
| Steakhouses that list it | — | 8 |
At a glance
- London broil
- A method, not a cut · today usually top round, the inside of the hind leg
- Flank steak
- Rectus abdominis, belly · 700 g / 25 oz–1.2 kg / 1.5–2.6 lb · 2–3 cm / ¾–1¼ in thick
- London broil pull at
- 52–54 °C / 126–129 °F, rest, then slice 3–5 mm
- Flank pull at
- 52–55 °C / 126–131 °F, 3–5 min a side
Is London broil a cut?
No. The phrase describes the cooking: “broil” is the American word for cooking under or over direct, intense heat, and London broil is a thick, lean steak marinated, broiled or grilled to rare or medium-rare and carved in thin slices across the grain. The name is American; there is no London dish of that name, and in British English the term is rarely used.
The first meat used for it was flank steak. The American cookery writer James Beard noted in 1974 that, until a few years earlier, London broil had meant only grilled flank, and that supermarkets were by then selling top round, sirloin and other cuts under the same name.
What is actually in the package?
Usually top round, 3–5 cm / 1¼–2 in thick, sometimes a piece of top sirloin, shoulder or bottom round. The USDA lists London broil among the common names of the top round steak. Top round (IMPS 168) is the largest muscle group on the inner side of the hind leg: the semimembranosus with the adductor alongside. It is called topside in Britain and Australia and nalga in Argentina.
Flank is a different animal part altogether: the rectus abdominis, a flat muscle along the lower belly, 2–3 cm / ¾–1¼ in thick and 700 g / 25 oz to 1.2 kg / 2.6 lb. One is the hind leg, the other the belly wall.
How do they compare side by side?
The table compares top round, the usual London broil, with flank steak.
| London broil (usually top round) | Flank steak | |
|---|---|---|
| What it is | A cooking method and a label | A cut |
| Muscle | Semimembranosus and adductor (top round) | Rectus abdominis |
| Location | Inside of the hind leg, the round | Lower belly wall |
| Thickness | Thick steak, 3–5 cm / 1¼–2 in | 2–3 cm / ¾–1¼ in |
| Grain | Long, even fibers; neat slices | Long and coarse along the whole piece |
| Fat | Very lean; almost no marbling | Lean; a thin membrane on each side |
| Pull at | 52–54 °C / 129 °F 126–129 °F | 52–55 °C / 131 °F 126–131 °F |
| Limit | Dries and firms above 60 °C / 140 °F 140 °F | Chewy at any temperature if cut with the grain |
| Spanish names | Nalga (Argentina), pulpa negra or cara (Mexico), tapa (Spain) | Flank; bife de vacío in Argentina (part of the vacío) |
| Classic dishes | London broil · deli roast beef | Fajitas · phở · ropa vieja |
How is each one cooked?
Both follow the same rules: marinate, cook hot and fast, never past medium-rare, rest, and slice thin across the grain.
For a top round London broil, marinate it, pat it dry, then broil it 8–10 cm / 3¼–4 in under a very hot broiler, turning once, until 52–54 °C / 126–129 °F inside. Rest about 10 minutes. Top round has almost no marbling to keep it moist, so the window between juicy and dry is narrow: above 60 °C / 140 °F the fibers squeeze out their water. A marinade does not rescue an overcooked piece. Very thick pieces cook more evenly with a reverse sear.
Flank is thinner and cooks in 3–5 minutes a side on a grill or in a hot pan, to 52–55 °C / 126–131 °F at the core. Its long, coarse fibers hold marinades well. Braised instead, it falls into long strands, the base of Cuban ropa vieja.
How is each one sliced?
Slicing does most of the work in both. Cutting the long fibers short is what makes them tender, and cutting with the grain leaves long strands to chew at any temperature.
Top round is cut thin, 3–5 mm, across the grain at a 45° angle. Flank is also cut across the grain at a low angle; its fibers run the full length of the muscle, so the knife goes across the width. The same top round, roasted whole and sliced paper-thin, is the classic deli roast beef.
Can one replace the other?
Yes, with adjustments. A London broil made from flank is the original version and cooks quickly because the muscle is thin. Top round is thicker and leaner, so it needs a thermometer more and a little longer under the heat, and it is less forgiving if overcooked.
Flank gives more beef flavor and a more open grain for marinades; top round gives neater, more uniform slices and is usually the more affordable of the two. Skirt can also stand in for flank in fajitas and stir-fries; see Skirt steak vs flank steak.
What to ask for at the counter
If the package says London broil, check the label for the cut: top round, top sirloin, shoulder or flank. If it is flank, ask for flank steak or, in Argentina, bife de vacío; in Britain and France bavette can mean either the flank or the flap. If it is top round, a lean cut is the point, so look for an even thickness of at least 3 cm / 1¼ in and avoid pre-marinated pieces that hide the color of the meat.
Keep reading
- Cut · Flank, long-grainedFlank steakThe flat belly muscle of fajitas, London broil and phở: never past medium-rare, always cut across the grain.
- Cut · Round, the leanest roastEye of roundA lean cylinder from the back of the leg: roast beef sliced thin, or the peceto, cuete and lagarto braised whole.
- Cut · Sirloin, the American meaningTop sirloinThe US sirloin: the rump's center muscle, lean and beefy, cooked fast. Not the British sirloin.
- Cut · Diaphragm, open grainSkirt steakThe diaphragm: thin, coarse-grained and deeply flavored. Cooked hot and fast, sliced across the grain.
Frequently asked questions
Is London broil the same as flank steak?
Not any more. London broil first meant broiled flank steak; now the name is mostly given to thick top round steaks, and flank steak is a different cut from the belly.
What cut is London broil?
Usually top round, the large inside muscle of the hind leg. Shops sometimes use the name for top sirloin or shoulder steaks, and originally it was flank.
Why is it called London broil?
The name is American and describes the method, broiling. There is no traditional London dish of that name.
Can I use flank steak for London broil?
Yes: flank was the original London broil. Marinate it, cook it hot to 52–55 °C / 126–131 °F and slice it thin across the grain.
Which is more tender, top round or flank?
Both are lean and tender only when cooked no further than medium-rare and sliced thin across the grain. Past 60 °C / 140 °F top round dries out; cut with the grain, flank is chewy.
Sources
7
- USDA Agricultural Marketing Service. Institutional Meat Purchase Specifications: Fresh Beef Series 100. Washington, DC, 2014. www.ams.usda.gov/sites/default/files/media/IMPS_100_Fresh_Beef%5B1%5D.pdf
- AUS-MEAT Limited. Handbook of Australian Meat, 7th ed. (International Red Meat Manual). Brisbane, 2005. www.ausmeat.com.au
- Agriculture and Horticulture Development Board (UK). Beef Meat Purchasing Guide. Kenilworth, 2016. ahdb.org.uk
- Instituto de Promoción de la Carne Vacuna Argentina (IPCVA). Cortes de carne vacuna argentina — nomenclatura y usos. Buenos Aires. www.ipcva.com.ar
- McGee, Harold. On Food and Cooking: The Science and Lore of the Kitchen, rev. ed. New York: Scribner, 2004.
- Huerta-Leidenz, Nelson. International Nomenclature Guide of Beef Cuts for the U.S.A. and Other Countries Targeted by the U.S. Meat Export Federation. Denver: U.S. Meat Export Federation, 2013. www.usa-beef.org/wp-content/uploads/2020/07/1064.GUIDE_beef-cuts_ingl%C3%A9s_09oct13.pdf
- Beard, James. Beard on Food. New York: Alfred A. Knopf, 1974.