Not all broilers are the same bird. That sounds obvious — yet plenty of producers still benchmark their Ross 308 flock against Cornish Cross data, then wonder why the numbers don’t add up. Each commercial strain has its own weight curve, its own optimal slaughter window, and its own tendency to allocate muscle versus fat at different stages of the grow-out.
This guide breaks down the ideal weight targets for the five most widely used broiler breeds and commercial hybrids, using a practical broiler weight chart by breed approach to explain what makes each strain perform differently, and gives you a framework for choosing the right breed for your production targets. Whether you’re running a high-throughput deboning operation or a small-scale pasture program, the weights in this comparison are the numbers you should actually be measuring against.
Why Breed Determines More Than Just Size
When someone asks about the average weight of a broiler chicken, there’s no single correct answer — there’s only a correct answer for a given strain under given conditions. A Cobb 500 at 35 days will typically weigh 15–18% less than a standard Cornish Cross at the same age. A Hubbard Flex at 42 days can be close to a Ross 308 in live weight, but will yield a meaningfully different breast muscle percentage.
This matters commercially because the calculation isn’t just live weight — it’s live weight vs dressed weight, breast yield percentage, leg quarter ratio, and what your processing contract actually pays for. A heavier live bird that dresses poorly can net you less per bird than a lighter one that yields well. which is why using a broiler weight chart by breed helps align production decisions with profitability.
Broiler Breed Weight Comparison: At-a-Glance
Target live weights at common slaughter ages, standard commercial conditions, mixed-sex flocks:
Breed-Strain / Day 35 (kg) / Day 42 (kg) / Day 49 (kg) / Typical FCR (35–42d) / Breast Yield
Ross 308 / 1.95–2.10 / 2.75–2.95 / 3.45–3.65 / 1.75–1.90 / 22–24%
Cobb 500 / 1.85–2.00 / 2.60–2.80 / 3.30–3.50 / 1.72–1.88 / 21–23%
Hubbard Flex / 1.70–1.90 / 2.45–2.65 / 3.15–3.35 / 1.78–1.95 / 20–22%
Cornish Cross / 1.80–2.05 / 2.65–2.90 / 3.40–3.60 / 1.80–1.98 / 22–24%
Arbour Acres Plus / 1.90–2.05 / 2.70–2.88 / 3.40–3.55 / 1.76–1.91 / 22–23%
Freedom Ranger / 1.20–1.45 / 1.65–1.90 / 2.20–2.50 / 2.10–2.35 / 17–19%
Freedom Ranger is included for reference — it’s a slow-growing strain primarily used in pasture and label rouge programs, not conventional commodity production. Its FCR and breast yield figures reflect a fundamentally different biological and commercial model.
Breed-by-Breed Breakdown
Ross 308: The Global Standard
The Ross 308 is the most widely deployed broiler strain in the world and acts as the de facto benchmark in most weight comparison discussions. It’s an Aviagen product, and its performance manual is one of the most detailed publicly available documents in commercial poultry production.
Key traits: excellent broiler chicken growth rate in the starter phase, strong breast muscle development, and consistent performance across a wide range of climates. The 308 tends to peak daily gain around day 30–34, which makes day-35 live weight one of its most competitive metrics against other strains, as reflected in a broiler weight chart by breed.
Ideal slaughter window: 35–42 days for whole-bird retail programs; up to 49 days for deboning operations. Beyond day 50, FCR deterioration accelerates and leg health issues become a more frequent concern.
Cobb 500: Feed Efficiency First
Cobb 500 is often positioned as the feed-efficiency champion. Its Cobb 500 broiler growth rate is slightly below Ross 308 in absolute terms, but its lower voluntary feed intake means it often achieves competitive FCR at lower feed cost per kilogram of gain — an important distinction in high-feed-cost environments. which becomes clearer when analysed using a broiler weight chart by breed.
The Cobb 500 broiler management guide (available from Cobb-Vantress) explicitly targets a live weight of 2.3–2.7 kg at 38–42 days under standard commercial density. If your flock is consistently undershooting that range, water management and feeder space are usually the first places to investigate.
One practical note: Cobb 500 tends to be slightly more sensitive to heat stress than Ross 308, which matters if your housing doesn’t have reliable evaporative cooling in summer months.
Cornish Cross: The Backyard and Small Farm Standard
In North American small-farm and homestead contexts, “broiler” essentially means Cornish Cross. The Cornish Cross weight chart is what most backyard producers compare against, even if they don’t always know it by that name. Though a broiler is reflected in a broiler weight chart by breed. provides a more accurate comparison across different strains.
Cornish Cross is a cross between Cornish and Plymouth Rock lines, optimised for rapid breast development. Cornish Cross weight at 8 weeks typically falls between 3.8 and 4.5 kg live, though most small-farm producers target slaughter between weeks 7 and 8 to avoid the leg and heart issues that become more prevalent as the bird gets heavier relative to its frame, which can be better managed using a broiler weight chart by breed.
Practical Tip:
If you’re raising Cornish Cross on pasture with daily rotation, add 5–7 days to your expected slaughter window compared to a confinement setup. Increased movement and variable weather slow the growth curve. That’s not a problem — it’s just a different target. Weigh a sample bird at day 42 and project forward from there rather than relying on a fixed calendar date.
Hubbard Flex: Versatility for Speciality Markets
Hubbard Flex occupies an interesting middle ground. It was developed specifically for producers who need flexibility in slaughter age — the strain holds weight plateau reasonably well between days 42 and 56 without the rapid FCR collapse seen in fast-growing hybrids. This makes it popular for operations where processing slot availability is unpredictable.
Hubbard broiler performance in the starter phase is slightly slower than Ross 308, but the strain compensates with better leg health scores and lower mortality rates at extended grow-out ages. For operations targeting heavier birds (3.5–4.5 kg live), Hubbard Flex is worth serious consideration. especially when evaluated alongside a broiler weight chart by breed to plan optimal slaughter timing.
Arbour Acres Plus: Breast Yield Without Compromise
Arbour Acres Plus (also an Aviagen product) is positioned as the high-yield counterpart to Ross 308. Its broiler chicken weight trajectory is very close to Ross 308, but it consistently outperforms on breast meat percentage — particularly in birds slaughtered above 2.8 kg live. If your contract includes a premium for breast yield, Arbour Acres Plus is the strain most likely to capture that premium consistently.
Live Weight vs Dressed Weight: What the Yield Numbers Actually Mean
Live weight is what your scale reads. Dressed weight is what your customer — or your processor — actually pays for. The ratio between them (dressing percentage) typically falls between 72% and 78% for conventional commercial broilers, depending on feed withdrawal time, processing line efficiency, and breed.
Breed / Avg Live Weight (42d) / Dressing % / Dressed Weight / Breast Yield (of live)
Ross 308 / 2.85 kg / 75–77% / 2.14–2.19 kg / 22–24%
Cobb 500 / 2.70 kg / 74–76% / 2.00–2.05 kg / 21–23%
Hubbard Flex / 2.55 kg / 73–75% / 1.86–1.91 kg / 20–22%
Cornish Cross / 2.80 kg / 74–76% / 2.07–2.13 kg / 22–24%
Freedom Ranger / 1.80 kg / 70–73% / 1.26–1.31 kg / 17–19%
Feed withdrawal before slaughter significantly affects dressing percentage — a 6-hour withdrawal removes most gut content (which is dead weight at the scale). Producers who measure live weight at slaughter after only 2–3 hours of feed withdrawal are systematically overestimating what they’ll actually yield.
How to Use This Comparison to Choose the Right Breed
Three questions narrow the decision quickly:
- What does your contract or customer actually pay for? If it’s live weight on a flat rate, growth speed and FCR dominate. If there’s a breast yield premium, Arbour Acres Plus or Ross 308 are the obvious starting points.
- What’s your slaughter age? For 35–38 day programs, Ross 308 and Cobb 500 are the strongest options. For 42–49-day programs, the gap narrows, and Hubbard Flex becomes more competitive. Beyond day 50, Hubbard Flex is the safer bet for leg health and consistent chicken weight. which can be more accurately planned using a broiler weight chart by breed.
- What’s your climate and housing quality? In high-heat environments without reliable cooling, Cobb 500’s heat sensitivity is a real operational risk. Ross 308 or Hubbard Flex may underperform less in those conditions.
- Are you in a conventional or alternative production system? Pasture, organic, and slow-growth certification programs almost always require slower-growing genetics (Freedom Ranger, Label Rouge strains). Running Cornish Cross or Ross 308 on a slow-growth label program will likely result in welfare and certification compliance issues regardless of broiler weight. Making a broiler weight chart by breed is essential for choosing compliant genetics.
Frequently Asked Questions
What is the ideal weight for a broiler chicken at slaughter?
For conventional commercial operations, the average weight of a broiler chicken at slaughter ranges from 2.4 to 3.2 kg live weight for whole-bird programs, and 3.2 to 4.0 kg for deboning-focused lines. The “ideal” weight is always relative to the processing contract specification, not an absolute number.
Which broiler breed grows the fastest?
In terms of absolute daily gain at peak growth (typically days 28–35), Ross 308 and Arbor Acres Plus consistently post the highest average daily gain in peer-reviewed performance comparisons. However, “fastest” in a commercial context should account for both growth speed and FCR — a slightly slower bird that eats 8% less feed per kg of gain may be more profitable than the fastest grower.
Is Ross 308 or Cobb 500 better?
The Ross 308 vs Cobb 500 debate doesn’t have a universal answer. Ross 308 tends to edge ahead on peak growth rate and breast yield. Cobb 500 often performs better on FCR in high feed-cost environments and may have a slight edge in markets where smaller bird size is preferred. In practice, regional hatchery availability often drives the decision as much as performance data does.
What is a normal Cornish Cross weight by week?
A standard Cornish Cross weight by week progression under good management: week 1 ~180 g, week 2 ~480 g, week 3 ~950 g, week 4 ~1.6 kg, week 5 ~2.4 kg, week 6 ~3.1 kg, week 7 ~3.7 kg, week 8 ~4.3 kg. Small-farm producers typically target slaughter at week 7–8 (3.5–4.2 kg live) to balance yield against leg health risk.
Interesting Fact: The “Cornish Cross” isn’t a registered breed — it’s a common name for any commercial broiler cross that involves Cornish genetics on the sire side. What backyard producers in North America call “Cornish Cross” are actually proprietary hybrids sold by hatcheries, similar in type to Ross and Cobb strains but produced from different parent lines. Two birds labeled “Cornish Cross” from different hatcheries can have noticeably different weight curves and leg health profiles.
Every number in this guide is only as useful as the data you’re comparing it against. The best broiler weight chart by breed in the world won’t tell you anything meaningful if your sampling is inconsistent, your scales aren’t calibrated, or you’re weighing at different times of day each week.
Accurate, repeatable weighing is the foundation of any serious performance benchmarking program — regardless of which strain you’re running. Find the right scale for your operation at poultryscales.com.
