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18 lb Brisket at 275°F

Wrapped in butcher paper, a 18 lb whole packer at 275°F runs about 15 h 5 m of cook time — plan 17 h 5 m door to table with a 2-hour rest. For dinner at 5 PM, put it on at 11:45 PM the day before. Adjust anything below and the plan recalculates.

Brisket Cook Time Calculator

Put it on at

11:45 PMthe day before

Total time
17 h 5 m (15 h 5 m cook + 2 h rest)
Realistic range
15 h 15 m – 18 h 50 m
Pit temperature
Wrap
Cut
Rest / hold (hours)

Your timeline

  1. 11:45 PMBrisket on the smoker · the day before
  2. 6:32 AMStall begins (~150–170°F internal)
  3. 8:02 AMWrap it
  4. 1:19 PMStart probing for tenderness
  5. 2:49 PMPull it (~203°F, probe-tender)
  6. 5:00 PMSlice and serve

Planning estimates at ±12% — thickness matters more than weight, and no two briskets cook alike. The clock never decides when it's done: brisket is done when a probe slides into the thickest part of the flat like warm butter, around 203°F internal. Cook to feel, serve on time by resting longer — a wrapped brisket holds beautifully for hours.

When to start a 18 lb brisket at 275°F

Butcher paper wrap, whole packer, 2-hour rest. Start times round down to the quarter hour — early is free, late is dinner at nine.

Serving atPut it on at
12:00 PM lunch6:45 PM · the day before
3:00 PM9:45 PM · the day before
5:00 PM11:45 PM · the day before
7:00 PM1:45 AM

Wrapped or naked at 275°F?

Wrapping shortens the stall. Foil is fastest but softens bark; butcher paper is the standard compromise; no wrap costs time and buys crust.

WrapCook timeWith 2 h rest
Butcher paper~15 h 5 m~17 h 5 m
Foil (Texas crutch)~13 h 45 m~15 h 45 m
No wrap~16 h 10 m~18 h 10 m

Cooking a flat instead of a whole packer? A trimmed flat is thinner and finishes faster — figure about 13 h 35 m at 275°F in paper.

275°F: hot and fast

275°F is the hot-and-fast school — the temperature many Texas joints quietly run because time is money. At 0.9 hours per pound, a 18 lb packer finishes in about 15 h 5 m wrapped in paper. That turns brisket from an overnight commitment into a same-day cook.

The trade is attention. Everything moves faster at 275°F, including the window between perfect and overdone, so probe earlier than you think you need to and trust feel over the clock. Wrapping is close to mandatory here — the bark sets fast, and paper keeps the flat from drying while the point finishes.

A 18 lb packer is a big brisket. Thickness, not weight, is what really sets cook time, and big packers are thick — hold the estimate loosely, expect the stall to drag, and lean on the built-in hold if it finishes early.

How many people does a 18 lb brisket feed?

Trimming and a long cook take roughly half the raw weight, so a 18 lb packer yields about 9 lbs of sliced brisket. Plated at half a pound per adult, that is 18 people; chopped into sandwiches at a third of a pound, closer to 27 servings. Feeding a crowd near 20? The brisket for 20 people page does the shopping math, and the portion calculator handles kids, sides, and leftovers.

Quick answers

How long does a 18 lb brisket take at 275°F?

About 15 h 5 m wrapped in butcher paper, or 16 h 10 m unwrapped — plan 17 h 5 m total with a 2-hour rest. The honest range is 15 h 15 m to 18 h 50 m, because thickness matters more than weight and no two briskets cook alike.

When should I start a 18 lb brisket at 275°F for dinner at 5 PM?

Put it on at 11:45 PM the day before. That includes the cook plus a 2-hour rest, and the start time is rounded down to the quarter hour — starting early is free, because a wrapped brisket holds for hours.

How many people will a 18 lb brisket feed?

A 18 lb raw packer yields roughly 9 lbs of sliced brisket after trimming and cooking — about 18 adults as a plated main at half a pound each, or around 27 sandwiches at a third of a pound each.

Other briskets at 275°F