Pig Weight by Age — What to Expect Week by Week

Why Tracking Pig Weight by Age Matters

A pig that falls 15 lbs behind the average at eight weeks will often finish 25–30 lbs light at market — costing you real money. Conversely, a pig tracking ahead of schedule can be marketed earlier, freeing pen space and cutting feed costs. Weekly weight checks, even approximate ones, give you the data to act before small problems become expensive ones.

The figures below are benchmarks for well-managed commercial crossbreds (Yorkshire × Landrace × Duroc type). Purebreds, heritage breeds, and poorly nourished pigs will vary — sometimes significantly. Use these numbers as a compass, not a contract.

Piglet Weight: Birth to Weaning (Weeks 0–4)

A healthy newborn piglet weighs between 2.5 and 3.5 lbs (1.1–1.6 kg). Birth weight is one of the strongest predictors of survival and lifetime growth performance. Piglets born under 2 lbs face significantly higher mortality risk in the first 72 hours.

During the nursing phase, a well-nourished piglet roughly doubles its birth weight by the end of week one and continues growing at approximately 0.4–0.6 lbs per day. Sow milk quality and litter size both drive how fast individual piglets grow — smaller litters tend to produce heavier weaners because competition for teats is lower.

Age	Typical Weight (lbs)	Typical Weight (kg)
Birth	2.5 – 3.5	1.1 – 1.6
1 week	5 – 7	2.3 – 3.2
2 weeks	9 – 13	4.1 – 5.9
3 weeks	13 – 18	5.9 – 8.2
4 weeks (weaning)	15 – 22	6.8 – 10.0

Starter Phase: Weeks 4–8

The transition from sow's milk to solid feed is stressful. Most pigs experience a growth check at weaning — a period of one to five days where intake drops and daily gain slows or temporarily reverses. Producers who minimize weaning stress (through consistent temperature, ad-lib water, and high-quality starter rations) see this check disappear quickly.

Once the pig adapts to solid feed — typically by day 7 post-weaning — average daily gain (ADG) climbs toward 1.0–1.3 lbs per day (0.45–0.59 kg/day). A pig at eight weeks should weigh 40–55 lbs (18–25 kg) under good management.

Grower Phase: Weeks 8–16

This is the most energy-efficient growth phase. Feed conversion ratios are favorable, and the pig is laying down lean muscle rapidly. ADG during this phase typically runs 1.5–1.8 lbs per day (0.68–0.82 kg/day).

Age	Typical Weight (lbs)	Typical Weight (kg)
8 weeks (2 months)	40 – 55	18 – 25
10 weeks	55 – 75	25 – 34
12 weeks (3 months)	75 – 100	34 – 45
14 weeks	95 – 125	43 – 57
16 weeks (4 months)	115 – 150	52 – 68

Finisher Phase: Weeks 16–24

As the pig's frame fills out, daily gain typically holds at 1.8–2.2 lbs per day (0.82–1.0 kg/day), though feed conversion worsens — it takes more feed per pound of gain than in the grower phase because a larger proportion of gain is fat rather than lean muscle.

Most commercial operations target a market weight of 240–280 lbs (109–127 kg) live weight, reached at roughly 22–26 weeks of age. Butcher hogs for direct retail are often marketed lighter — 200–220 lbs live — for a higher lean-to-fat ratio.

Age	Typical Weight (lbs)	Typical Weight (kg)
18 weeks	155 – 185	70 – 84
20 weeks (5 months)	185 – 215	84 – 98
22 weeks	210 – 245	95 – 111
24 weeks (6 months)	230 – 270	104 – 122
26 weeks	255 – 295	116 – 134

What Affects Pig Growth Rate?

Benchmark tables tell you what's typical — but several variables can push your pigs above or below those numbers:

• Genetics. High-index commercial lines from major breeding companies routinely achieve ADG above 2.0 lbs/day in the finisher phase. Heritage breeds like Berkshire and Large Black typically grow 20–30% slower but produce different carcass quality.
• Nutrition. Energy and lysine density in the diet are the two biggest dietary levers. Under-spec rations — especially protein-deficient ones — cap lean growth regardless of genetics.
• Health status. PRRS, ileitis, and respiratory disease are the most common causes of pigs falling significantly behind weight targets. A pig that's been sick for a week often needs two weeks of catch-up.
• Environment. Pigs are thermoregulatory athletes. When temperatures drop below the pig's thermoneutral zone (about 60–70°F for finishing pigs), they burn extra calories just staying warm — calories that would otherwise go into gain.
• Pen density. Overcrowded pens reduce feeder access time, increase stress, and can cut ADG by 10–15% even without visible health problems. The USDA recommends a minimum of 8 sq ft per pig at market weight.
• Sex. Barrows (castrated males) generally grow slightly faster than gilts and carry more backfat. Intact boars grow fastest of all but are rarely raised to market in the US due to boar taint concerns.

Using the Heart Girth Formula to Track Growth

If you don't have access to a livestock scale, you can track pig growth reliably using the heart girth tape method. Measure heart girth and body length every two weeks and enter the numbers into our free calculator. You'll get an estimated live weight that's typically accurate within ±5% — accurate enough to confirm whether your pigs are on track or falling behind.

The formula — Weight (lbs) = Heart Girth² × Body Length ÷ 400 — was developed by agricultural extension services and is validated for pigs between roughly 30 and 350 lbs. Outside that range, accuracy decreases.