How Much Grilled Steak for 20 People — Flank vs. Sirloin Quantities can feel like a math test right when you just want to light the grill. The cut you choose changes how much you should buy, and trimming loss matters more than you think. I’ll break down exact raw weights, cooking yield, and slicing strategies for both cuts. By the end, you’ll have a clear shopping list and a simple plan for stress-free grilling.

Start Here: Portion Math That Actually Works

For steak-forward meals with sides, aim for 8–10 oz cooked steak per adult. Lighter eaters and heavy sides? Use 6–8 oz. Teen athletes and steak superfans? Budget 10–12 oz.

• Target cooked total for 20: 12.5–15 lb
• Typical shrinkage: Flank ~25–28%; Top sirloin ~20–22%
• Raw buy for 20 (baseline 8–10 oz cooked):
  • Flank: 16.5–19.5 lb raw
  • Top sirloin: 15.5–18.5 lb raw

Flank vs. Sirloin: What Changes the Quantity

Both are lean, beefy, and grill-friendly, but they behave differently on the scale and the plate. That affects how much you buy.

Flank Steak (lean, long fibers, best sliced thin)

• Trim loss: Usually minimal, but moisture loss is higher.
• Cook temp: Best at medium-rare to medium to keep it tender.
• Serving style: Always slice thinly across the grain. Feeds people efficiently in tacos, salads, and platters.
• Buy this much: For 20, plan 9–10 oz cooked each → about 16.5–19.5 lb raw.

Top Sirloin (versatile, sliceable, better moisture retention)

• Trim loss: Modest; often sold nicely cleaned.
• Cook temp: Forgiving at medium; stays juicy in thicker slices.
• Serving style: Slice across the grain, slightly thicker than flank.
• Buy this much: For 20, plan 8–9 oz cooked each → about 15.5–18.5 lb raw.

Exact Shopping Lists (By Scenario)

Not every crowd eats the same way. Match your buy to the menu.

If Steak Is the Star (few heavy sides)

• Flank: 18–20 lb raw (about 8–10 average flanks)
• Top sirloin: 17–19 lb raw (one whole 17–18 lb sirloin subprimal or multiple 2–3 lb roasts)

If It’s Part of a Mixed Grill (chicken, sausages, shrimp)

• Flank: 12–14 lb raw
• Top sirloin: 11–13 lb raw

For Taco Bars, Salads, or Sliced Platters (plus hearty sides)

• Flank: 14–16 lb raw
• Top sirloin: 13–15 lb raw

Pro move: Buy 10% extra if you don’t know your crowd. Leftover grilled steak makes elite sandwiches and grain bowls.

Grilling and Slicing Tips That Stretch Your Steak

How you cook and cut the steak can save pounds at the store.

• Marinate smart: Acids and salt improve juiciness. A 30–120 minute soak helps flank especially.
• High heat, fast cook: Sear at 500–600°F. Pull flank at 125–130°F and sirloin at 128–132°F; rest 8–10 minutes.
• Slice across the grain: Flank should be very thin (1/8–1/4 inch). Sirloin can be slightly thicker (1/4–3/8 inch).
• Hold warm without drying: Slice, then toss with warm pan juices or a splash of beef stock. Cover loosely with foil.
• Season at scale: Roughly 1–1.25 tsp kosher salt per lb of raw beef. Go lighter if marinating overnight.

Sample Timeline for 20 People

1. 24 hours out: Shop, trim as needed. Marinate flank; dry-brine sirloin (salt only) on a rack.
2. 4 hours out: Pull meat to fridge front so it’s not ice-cold. Prep sides and sauces.
3. 1 hour out: Preheat grill to high. Set up a medium zone for finishing.

li>30 minutes out: Pat steaks dry, oil lightly, season. Set out cutting boards with sharp slicers.

4. Grill time: Sear, temp-check, rest 8–10 minutes.
5. Service: Slice across the grain, pan-juice splash, platter with tongs.

Flavor Boosters That Make Less Feel Like More

Big flavor means smaller portions still satisfy. Two winners:

• this chimichurri recipe adds brightness that flatters lean cuts
• a smoky coffee rub gives sirloin steakhouse depth

Serving trick: Offer 2–3 sauces: chimichurri, garlic-herb butter, and a peppercorn drizzle. Guests take less meat when toppings shine.

From My Kitchen: What Actually Works

I’ve fed groups of 25+ with both cuts, and the biggest saver is how thin you slice flank. When I kept slices at 1/8 inch, the same raw weight stretched 10–15% further than thicker cuts. I also stopped over-marinating: more than 6 hours with strong acid made the outer layer mushy and “shrinky,” which looked like less food on the platter. For sirloin, I dry-brine overnight and finish with a warm butter baste—people take smaller portions because it eats richer. Finally, I now pre-slice half the steak before guests arrive; it controls portions better than on-demand carving.

Frequently Asked Questions

How much grilled steak for 20 people if it’s the main course?

Plan on 8–10 oz cooked per person. That’s 12.5–15 lb cooked total. Buy 16–20 lb raw depending on the cut and how much you expect it to shrink.

Should I buy more flank or sirloin for a crowd?

Flank loses slightly more moisture, so you’ll buy a bit more. Expect roughly 16.5–19.5 lb raw flank versus 15.5–18.5 lb raw top sirloin to feed 20 with steak as the star.

What’s the best way to slice flank and sirloin for 20 people?

Rest 8–10 minutes, then slice across the grain. Keep flank very thin (1/8–1/4 inch) and sirloin slightly thicker (1/4–3/8 inch). Thinner slices go further and stay tender.

Can I make grilled flank or sirloin ahead of time?

You can grill up to 1 hour ahead. Slice, toss with warm juices, and hold covered at low heat or in a warm oven (around 170–180°F). For longer, grill to 5°F under target and rewarm gently before slicing.

How do I keep grilled steak juicy on a buffet?

Slice just before serving, then toss with pan juices or a splash of warm beef stock and butter. Keep covered, vented slightly, and avoid direct heat in chafers—use hot water pans beneath to prevent drying.

What sides reduce how much steak I need?

Serve hearty fillers: grilled vegetables, potato salad, beans, cornbread, and a big grain salad. With two substantial sides, you can target 6–8 oz cooked steak per person.

The Bottom Line

For 20 people, budget 12.5–15 lb cooked steak: slightly more raw for flank than sirloin. Nail the sear, rest, and thin slicing, and your platters will look (and eat) generous without overbuying.

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