(What, like it’s hard?) Legally Blonde memes aside, 21-inch biceps aren’t that big … if you’re backstage at an Arnold Classic, Mr. Olympia, or Mr. Universe competition.
Five-time Mr. Olympia finalist Roelly Winklaar would still outsize you by a full three inches. But 21-inch unflexed upper arms would land you in “genetic freak” territory — an insane 7.59 inches (or 44.1%) larger than the average 20–29-year old.
You wouldn’t be the first guy to budge the tape to 21 inches.
But is it physically possible to do it naturally?
Table of Contents
- Yes, 21-Inch Biceps Are Possible (But Realistic?)
- Either Way, Blame Genetics
- 21-Inch Biceps Take Years, If Not Decades
- Training For Maximum Arm Size
- Fueling Your Body For Maximum Arm Size
Yes, 21-Inch Biceps Are Possible (But Realistic?)
Legend has it, the Lunk Alarm at Planet Fitness will blare if you even think about walking into a PF club with 21-inches hanging at your sides. OK, joking aside, what are the odds of actually stretching the measuring tape a full 21 inches?
Let’s start with a few examples of those who’ve eclipsed the 21-inch mark.
John “Mountain Dog” Meadows
Better known as “Mountain Dog” and the creator of Baby Groot, the late John Meadows was nearly 215 pounds of pure muscle. The on-stage powerhouse sculpted impressively lean 21-inch arms over his 30-year bodybuilding career, appearing even larger on his 5’6” physique.
Mike O’Hearn starred as Thor in the original American Gladiators (‘89–’96) and tied Ferrigno and Schwarzenegger with four Mr. Universe titles. At a towering 6’3” with 21-inch biceps, the veteran bodybuilder is known for his intimidating size and Power Bodybuilding programs.
A Full 1 ½ Inches Bigger Than Arnold Schwarzenegger
Out of respect, we won’t speculate on whether Meadows or O’Hearn owe their 21-inch club memberships to anabolic steroids. But we will offer a little perspective: Arnold Schwarzenegger.
The Austrian Oak captured his first of seven Mr. Olympia titles in 1970 when he was just 23 years old. The youngest Mr. Olympia victor in history (still) and the six-time back-to-back champion, Schwarzenegger confessed to using anabolic steroids while “cutting up” in the ‘70s.
Despite that and claiming to have 22–23-inch pythons, his real upper-arm measurement — according to Arthur Jones — was 19 ¾ inches pumped. Cold and with PEDs, his biceps were closer to 19 ½ inches in circumference, or 1 ½ inch smaller than your biceps goal.
Unfortunately, Most 20+-Inch Biceps Aren’t Natural
By “natural,” we don’t mean the dopes injecting themselves with Synthol to artificially inflate their upper arms despite having questionable thin 11-inch forearms … or steroids. Mostly steroids.
There’s a reason most men won’t ever exceed 15, 16, or 17-inch biceps, let alone 19 or 21: it’s extremely difficult to do so without hitting the genetic lottery or turning to anabolic or androgenic steroids. (We’ll talk about why next.)
Many members of the exclusive 20+ club — including legends like Lou Ferrigno, Ronnie Coleman, Flex Wheeler, and Dorian Yates — admit to using PEDs to increase their size.
So unless a modern bodybuilder fails a pre-competition drug test or an old-school bodybuilding legend admits to using PEDs, we’ll never truly know who’s “natty” or “juice.” But it’s probably not a coincidence that you don’t know very many guys with 21-inch biceps.
Either Way, Blame Genetics
It’s only human nature to blame DNA for traits “out of our control,” from dark-colored hair and hitchhiker’s thumb to beer bellies and sneezing in sunlight (that’s real).
If you blame your ancestors for your bony biceps, you’re not too far off either. Research from 2009 suggests that up to 50–80% of your lean mass potential is purely genetic.
Whether you’ll sprout 21-inch biceps or max out at 16 depends on genetic factors like:
As it turns out, mutated DNA isn’t always a bad thing.
The MSTN gene controls the protein called “myostatin.” Without getting too caught up in the details, myostatin blocks skeletal muscle from growing too large in normal DNA sequences.
However, a mutation to this gene can cause a condition known as myostatin-related muscle hypertrophy. This medical phenomenon curbs body fat levels while also supporting up to twice as much muscle for a naturally lean, muscular physique.
ACTN3 is one of the most talked-about genes in bodybuilding circles due to its impact on protein synthesis, fiber type, and muscle damage.
Those with ACTN3 expressed as “RR” tend to have more fast-twitch (power-based) muscle fibers, greater strength, more size potential, and less muscle-tearing post-exercise.
The XX or RX genotypes won’t screw you over with twiggy arms for life. But if your end goal is 20-and-up biceps, your ACTN3 genotype can determine how realistic that is.
Muscle Belly Size
Psychologist William Sheldon introduced the concept of somatotypes in the 1940s, claiming that the human body takes on one of three shapes: ectomorphic (tall and thin), mesomorphic (strong and fit), and endomorphic (short and heavy).
Research shows that somatotype is at least partially genetic. But what’s most interesting here is the possible link between body shape, muscle bellies, and tendon length. (We’ll explain!)
Like other skeletal muscles, the biceps brachii has a tendon on either side connecting the muscle to the bones and a “belly” — or muscle fibers. “Long” biceps have a shorter tendon connecting the belly to the elbow and are “superior” for adding more mass to the arm.
If you can only fit <2 finger-widths between your flexed biceps and your elbow, your odds of growing larger biceps are slightly better. (Though you’ll still need to hit the genetic lottery.)
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21-Inch Biceps Take Years, If Not Decades
The biceps can take anywhere from six weeks to a full year to grow a solid inch. But that doesn’t mean 21-inches are just 48–416 weeks away if you’re stuck at a flat-13.
If you’re genetically capable of surpassing the 21-inch milestone, you likely won’t know for years (or possibly decades) because:
Muscle Growth Isn’t Consistent
Physiologist Lyle McDonald is an expert in aesthetic physiques and the creator of Body Recomposition. In his McDonald Model for Genetic Muscular Potential, he suggests that annual mass gain potential drop by half with each year of proper resistance training:
A newbie may stretch the tape around their biceps an extra two inches in a year. That rate also implies a single inch of growth in year two, ½ an inch in year three, and so on.
McDonald predicts that the male physique will max out at about 40–50 pounds of lean mass after 4+ years of training. If you are genetically capable of 21-inch biceps, the progress will be remarkably slow after year one (the newbie gains) and two.
Each Inch Requires +10–15 Pounds of Lean Mass (Right?)
Charles Poliquin is another bodybuilding genius credited with training Olympic athletes across dozens of disciplines.
The trainer theorized that you need to gain 10–15 pounds of mass to increase your arm size by one inch. (After a few rounds through the grapevine, it’s not exactly clear whether that’s 10–15 pounds of lean mass or any extra poundage.)
Poliquin also insisted that after exceeding 18 inches, the required weight gain runs closer to 25 pounds per inch. Let’s say this is true (even though it’s purely anecdotal). If you have 13-inch flexed biceps right now, you’d need to pack on at least 125 pounds.
Most 21-Inch Biceps Aren’t Lean
Most members of the elite 21-inch club aren’t built like Mike O’Hearn or John Meadows (AKA: extremely muscular with <9% body fat). But the easiest and most common method for exiting 20-inch territory is also a technicality — gaining body fat.
Strength coach Steve Shaw revealed his own formula for predicting a reasonable natural arm size by body fat percentage.
If you’re currently <15% body fat, add 10 to your wrist circumference. For every four percentage points, you climb above 15%, your (predicted) maximum arm potential grows by ½-inch:
- 16–20%: Add 10.5 to your wrist circumference
- 21–25%: Add 11 to your wrist circumference
- 26–30%: Add 11.5 to your wrist circumference
- 31–35%: Add 12 to your wrist circumference
- 36–40%: Add 12.5 to your wrist circumference
- 41%+: Add 13 to your wrist circumference
Like McDonald’s formula and Poliquin’s theory, Shaw’s method isn’t an exact science and is dependent on several factors. But if simply saying “I have 21-inch biceps” is all that matters to you, the obvious solution is gaining any type of weight.
We Have to Talk About Proportions…
Don’t call us “wet blankets,” but 21-inch arms aren’t exactly aesthetic by today’s standards. But for argument’s sake, let’s say that “Hercules” Steve Reeves’ formula for the ideal body proportions is — in fact — widely accepted as “attractive.”
Reeves had an obsession with proportions and what he considered “perfect” ratios between certain areas of the body (i.e., the chest and the pelvis, the thighs, and the knees).
According to Reeves, arm size should be 252% the size of the wrist (or 2.52x). By this logic, 21-inch arms would best pair with 8.33-inch wrists.
How does that work out mathematically in Reeves’ eyes?
A poll of 1,563 men unveiled something startling — a wrist circumference of 8.33 inches would land you somewhere between the 88th and 93rd percentile for wrist size. Or that 21-inch bazookas could look freakishly large on 88–93% of men.
(Again, this is 0% fact-based. But if we consider the Golden Era of Bodybuilding to be the most aesthetic of all, this might make you re-evaluate your 21-inch goal.)
Training For Maximum Arm Size
Your goal of building 21-inch biceps is at the mercy of your DNA, time, and weight gain potential — ironically, three factors completely out of your control. But it is possible to maximize your upper arm size, even if you fall several inches short of this elusive 21-inch-land.
Adding inches (and we mean real lean inches) to your upper arms means training all parts of these muscles separately and directly:
Quick anatomy lesson: the “biceps” are actually called the biceps brachii, the two-headed muscle running along the front of your upper arm that controls elbow flexion (pulling weight inward). For simplicity’s sake, we also lump another muscle into biceps training:
- The long head of the biceps brachii creates the illusion of a thicker, fuller peak when flexing. Recommended exercise: Incline dumbbell curls.
- The short head of the biceps brachii increases width along the inner biceps to sculpt a fuller-looking upper arm. Recommended exercise: Preacher curls
- The brachialis sits just beneath the biceps brachii and pushes the peak even higher. Recommended exercises: Reverse curls and hammer curls
Developing both heads of the triceps and the brachialis can add serious height and width to your upper arms. However, building your biceps is only half the battle (or more like 30–40%).
Another fun anatomy lesson: the “triceps” are a three-headed muscle that sits opposite your biceps, extends the elbow and is actually responsible for 60–70% of your total “biceps” size. To add inch after inch to your upper arms, you’ll also need to target all three heads:
- The long head of the triceps brachii is the innermost rear portion of the triceps. Recommended exercise: Overhead extensions
- The medial head of the triceps brachii is the smallest and lowest-sitting head of the triceps. Recommended exercise: Skullcrushers
- The lateral head of the triceps brachii is the longest and also reportedly the strongest of all three triceps’ heads. Recommended exercise: Cable pushdowns
On top of stretching the tape just a little bit further, triceps exercises can also carve out an aesthetic horseshoe shape along the back of your arm.
Hypertrophy Training Principles
The “secret” to escaping average arm territory isn’t partial reps (though they’re scientifically proven to increase triceps size), reverse pyramid training, or rep overload like Kris Gethin’s DTP. It’s training your muscles in a way they respond best.
In 2019, experts examined 30 hypertrophy-based studies to determine the best training principles for building lean mass. Check out the results below!
* This isn’t a “follow these rules or else” type of deal. You’re absolutely free to tweak these guidelines or even include drop sets, supersets, and low-load training to break through plateaus.
Fueling Your Body For Maximum Arm Size
Each curl and extension will leave behind microscopic tearing in your biceps and triceps. In the 48–72 hours after training, the body will release muscle-repairing hormones like testosterone and fuse the damaged fibers together to create fuller, denser muscles.
However, this isn’t possible without a proper diet and the right combination of sports supplements. So turn those softball-sized biceps into cannonballs and add definition to your triceps’ horseshoe with:
The Bodybuilder’s Diet
(Side note: It’s 100% possible to build muscle with a maintenance diet or while in a caloric deficit — or burning more calories than you eat. But a surplus is the most efficient method.)
We spent a decent section of this article bashing bodybuilders for their steroid use. But natural (like, real natty) bodybuilders are also a solid resource for men looking to maximize their lean mass without padding their arms with a layer of fat.
The classic bodybuilder’s diet in the off-season (or bulk cycle) is:
- Calories: Maintenance + 15%
- Proteins: 25–30%
- Carbohydrates: 55–60%
- Fats: 15–20%
Say you need 3,000 calories to maintain your current body weight. To add serious mass to your arms, you’d bump your daily calorie goal up to 3,450 and get 862.5+ calories from protein, 1,897+ from carbs, and the final 517.5 from fats.
Whey protein should never replace your protein intake from natural foods. But with 20–40g of protein-packed into a single scoop, whey powders can aid muscle recovery in the hours post-workout and help reach the recommended 0.5–0.8g of protein per pound of body weight.
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Pre-workout is one of the best ways to take your arm workouts to the next level, especially if the formula has a high caffeine level. Caffeine is a stimulant that can increase mental focus, strength, and explosive power during resistance training.
Not surprisingly, studies link caffeine pre-workout to increased mechanical work, power output, and bar velocity during a 4×8 bench press trial. The higher the volume and more micro-tearing within the arms, the larger they’ll grow post-recovery.
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Creatine is an amino acid that partially controls the energy within skeletal muscle, particularly during heavy-resistance training. The widely studied supplement also pulls water into the muscles to make them both feel and look denser.
Creatine’s impact on mid-workout energy and strength also aligns with its hypertrophy benefits. Plenty of studies — including this one from 2011 — link regular creatine use to significantly increased strength and muscle thickness.
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