Buying guide · Diaphragm vs belly

Skirt steak vs flank steak

Skirt steak and flank steak are both flat, long-fibred cuts from the underside of the steer, cooked hot and sliced across the grain, but they are different muscles. Skirt is the diaphragm, 1–2 cm thick, with the most open grain of any steak and more fat between its fibres; flank is the rectus abdominis of the belly wall, 2–3 cm thick and leaner, with fibres that run the full length of the piece.

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Also known as: Entraña (skirt) vs flank (bife de vacío) · Diềm thăn (skirt) và nạm bò (flank) · Hampe vs bavette de flanchetLast reviewed 25 Oct 20269 sources

Where does each one come from?

The skirt comes from inside the ribcage, where the chest ends; the flank comes from the outside of the belly, further back, below the loin.

Two muscles are sold as skirt. The outside skirt is the costal part of the diaphragm, the sheet of muscle that separates the chest from the abdomen; it lies against the inside of the sixth to twelfth ribs, on the plate, wrapped in a tough membrane, and is specified in the United States as IMPS 121C. The inside skirt is the transversus abdominis, a wider, thinner and leaner muscle on the abdominal wall next to the flank (IMPS 121D). Each side of the animal gives one outside skirt of about 600–900 g and one inside skirt of 900–1,300 g.

The flank steak is the rectus abdominis, the flat muscle that runs along the lower belly from the ribs to the hip. It has no neighbouring bone and is lifted out as a single flat muscle of 700 g to 1.2 kg (1.5–2.6 lb), one per side, with a thin membrane on each face that butchers remove (IMPS 193, HAM 2210). Argentine butchery usually keeps it inside the vacío, the whole belly wall; lifted out, it is sold as bife de vacío.

How do they compare side by side?

Skirt is thinner, looser and fattier; flank is thicker, tighter and leaner. The table sets out the other differences.

What are they called in each country?

In the United States both keep their English names; in Argentina the outside skirt is the entraña and the flank, part of the vacío, is bife de vacío; in France they are hampe and bavette de flanchet.

Several names cross over. In Britain and France “bavette” may mean the flank or the flap beside it; Brazil's fraldinha is the flank and flap, not the skirt; American supermarket fajita meat is skirt, often the inside skirt, or strips of flank. And “thick skirt” in Australia is not a skirt at all but the hanger, compared in Hanger steak vs skirt steak.

How is each one cooked?

Both are cooked hot and fast and taken off at 52–55 °C / 126–131 °F in the centre: the skirt in 2–3 minutes a side, the thicker flank in 3–5 minutes a side. Both rest for a few minutes before slicing.

The skirt goes onto the hottest part of the grill or a smoking pan. Cooked much past medium, its thin fibres tighten and turn to leather. Its open structure takes a marinade in minutes rather than hours, though it needs none: in the Río de la Plata it is simply salted and grilled membrane side first, so the membrane crisps, and in Japan harami is cut into bite-sized pieces and grilled at the table over charcoal.

The flank, lean and even, is never taken past medium-rare. It takes marinades well, which is why it is the cut of London broil and of many fajitas. In Vietnam it is simmered whole in phở broth and sliced as nạm, or sliced paper-thin and dropped raw into the boiling broth; braised for a long time, it falls apart into the long strands of Cuban ropa vieja.

One can replace the other in fajitas, stir-fries and steak salads, provided the cooking time follows the thickness. Doneness targets are in Steak temperatures.

How is each one sliced?

Both are sliced thin across the grain; sliced along the grain, either is chewy at any temperature.

The direction of the grain is what differs. In the skirt the fibres run across the width of the long strip, so the steak is first cut into pieces 10–15 cm long and each piece is then turned and sliced thin across its fibres. In the flank the fibres run the length of the piece, so it is sliced across its width, at a low angle to the board, which gives wider, neater slices.

How much usable meat does each one give?

Across 38 batches of flank (162.5 kg) broken down by the Steakpedia Field Kitchen, 66 % of the weight became steaks, about 660 g per kilo bought, and 73.1 % was usable; the skirt has not been measured in enough pieces to give a figure.

Of the flank's weight, 12.8 % was fat trimmed off before portioning and about 14 % membrane, sinew and loss; another 7 % was meat for stir-fries, fajitas or mince. The spread between batches was wide, from 40 % to 89 % of steaks, which is what thin ends and membranes do to a flat muscle. Skirt, especially outside skirt, carries more fat between its fibres, and outside skirt sold membrane-on loses that membrane too, but without measured sheets Steakpedia gives no figure. The flank breakdown is in the flank steak article.

Frequently asked questions

Sources

9

1. 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
2. AUS-MEAT Limited. Handbook of Australian Meat, 7th ed. (International Red Meat Manual). Brisbane, 2005. www.ausmeat.com.au
3. Agriculture and Horticulture Development Board (UK). Beef Meat Purchasing Guide. Kenilworth, 2016. ahdb.org.uk
4. Instituto de Promoción de la Carne Vacuna Argentina (IPCVA). Cortes de carne vacuna argentina — nomenclatura y usos. Buenos Aires. www.ipcva.com.ar
5. Brasil, Ministério da Agricultura, SIPA. Portaria nº 5, de 8 de novembro de 1988 — Padronização de cortes de carne bovina.
6. Larousse Gastronomique, rev. ed. London: Hamlyn, 2009.
7. Japan Meat Grading Association. Beef Carcass Grading Standard. Tokyo, 1988 (rev. 2014). www.jmga.or.jp
8. McGee, Harold. On Food and Cooking: The Science and Lore of the Kitchen, rev. ed. New York: Scribner, 2004.
9. Steakpedia Field Kitchen. Butchery records, July–October 2026: 279 sheets, 1,604.6 kg of meat processed, weighed piece by piece on a calibrated scale and logged per cut. Open data, CC BY 4.0. steakpedia.com/field-data